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  • Using memory mapping in C for reading binary

    - by user1320912
    I am trying to read data from a binary file and process it.It is a very large file so I thought I would use memory mapping. I am trying to use memory mapping so I can read the file byte by byte. I am getting a few compiler errors while doing this. I am doing this on a linux platform #include <unistd.h> #include <sys/types.h> #include <sys/mman.h> int fd; char *data; fd = open("data.bin", O_RDONLY); pagesize = 4000; data = mmap((caddr_t)0, pagesize, PROT_READ, MAP_SHARED, fd, pagesize); The errors i get are : caddr not initialized, R_RDONLY not initialized, mmap has too few arguments. Could someone help me out ?

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  • implicit declaration of function usleep

    - by ant2009
    gcc (GCC) 4.6.3 c89 Hello, I am trying to use usleep. However, I keep getting the following warning: implicit declaration of function usleep I have included the unistd.h header file. The man pages mentions something about this. But I am not sure I understand by it: usleep(): Since glibc 2.12: _BSD_SOURCE || (_XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED) && !(_POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700) Before glibc 2.12: _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED But not sure what I a to do with the above? Many thanks for any suggestions,

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  • Using write to print floating point numbers.

    - by Tom
    Hi, As an exercise to achieve something larger, i'm trying to use write to print a floating point number. I haven't done this in a while. I must be doing something wrong because I cant get it to work. Here is my code #include <unistd.h> int main(){ float f = 4.5; write(1,&f,sizeof float); return 0; } However, when running it im getting ?@ Any thoughts? Thanks in advance.

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  • Sockets: Transport endpoint is not connected on send

    - by TheoretiCAL
    I'm trying to learn socket programming from http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html and am attempting to build a SOCK_STREAM client/server. My client: #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> #define SERVERPORT "4951" // the port users will be connecting to int main(int argc, char *argv[]) { int sockfd; struct addrinfo hints, *servinfo, *p; int rv; int numbytes; if (argc != 3) { fprintf(stderr,"usage: talker hostname message\n"); exit(1); } memset(&hints, 0, sizeof hints); hints.ai_family = AF_UNSPEC; hints.ai_socktype = SOCK_STREAM; if ((rv = getaddrinfo(argv[1], SERVERPORT, &hints, &servinfo)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); return 1; } // loop through all the results and make a socket for(p = servinfo; p != NULL; p = p->ai_next) { if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) { perror("talker: socket"); continue; if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) { close(sockfd); perror("client: connect"); continue; } } break; } if (p == NULL) { fprintf(stderr, "talker: failed to bind socket\n"); return 2; } if ((numbytes = send(sockfd, argv[2], strlen(argv[2]), 0) == -1)) { perror("talker: send"); exit(1); } freeaddrinfo(servinfo); printf("talker: sent %d bytes to %s\n", numbytes, argv[1]); close(sockfd); return 0; } Server: #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> #define MYPORT "4951" // the port users will be connecting to #define MAXBUFLEN 100 static int backlog = 10; // get sockaddr, IPv4 or IPv6: void *get_in_addr(struct sockaddr *sa) { if (sa->sa_family == AF_INET) { return &(((struct sockaddr_in*)sa)->sin_addr); } return &(((struct sockaddr_in6*)sa)->sin6_addr); } int main(void) { int sockfd; struct addrinfo hints, *servinfo, *p; int rv; int numbytes; int new_fd; socklen_t addr_size; struct sockaddr_storage their_addr; char buf[MAXBUFLEN]; char s[INET6_ADDRSTRLEN]; memset(&hints, 0, sizeof hints); hints.ai_family = AF_UNSPEC; // set to AF_INET to force IPv4 hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; // use my IP if ((rv = getaddrinfo(NULL, MYPORT, &hints, &servinfo)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); return 1; } // loop through all the results and bind to the first we can for(p = servinfo; p != NULL; p = p->ai_next) { if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) { perror("listener: socket"); continue; } int yes=1; // lose the pesky "Address already in use" error message if (setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(int)) == -1) { perror("setsockopt"); exit(1); } if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) { close(sockfd); perror("listener: bind"); continue; } if (listen(sockfd,backlog) == -1){ close(sockfd); perror("listener:listen"); continue; } break; } if (p == NULL) { fprintf(stderr, "listener: failed to bind socket\n"); return 2; } freeaddrinfo(servinfo); printf("listener: waiting to recv..\n"); while(1){ addr_size = sizeof their_addr; if ((new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &addr_size))==-1){ perror("accept"); exit(1); } if ((numbytes = recv(new_fd, buf, MAXBUFLEN-1 , 0) == -1)) { perror("recv"); exit(1); } printf("listener: got packet from %s\n", inet_ntop(their_addr.ss_family, get_in_addr((struct sockaddr *)&their_addr), s, sizeof s)); printf("listener: packet is %d bytes long\n", numbytes); buf[numbytes] = '\0'; printf("listener: packet contains \"%s\"\n", buf); close(sockfd); } return 0; } Upon executing the client, I get " send: Transport endpoint is not connected" and I'm not sure where I went wrong. Thanks.

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  • What is a cross-platform way to get the current directory?

    - by rubenvb
    I need a cross-platform way to get the current working directory (yes, getcwd does what I want). I thought this might do the trick: #ifdef _WIN32 #include <direct.h> #define getcwd _getcwd // stupid MSFT "deprecation" warning #elif #include <unistd.h> #endif #include <string> #include <iostream> using namespace std; int main() { string s_cwd(getcwd(NULL,0)); cout << "CWD is: " << s_cwd << endl; } I got this reading: _getcwd at MSDN getcwd at Kernel.org getcwd at Apple.com There should be no memory leaks, and is should work on a Mac as well, correct?

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  • Understanding behaviour of read() and write()

    - by neo730
    hi i am a student and just start learning low level c programming.i tried to understand read() and write() methods with this program. #include <unistd.h> #include <stdlib.h> main() { char *st; st=calloc(sizeof(char),2);//allocate memory for 2 char read(0,st,2); write(1,st,2); } i was expecting that it would give segmentation fault when i would try to input more than 2 input characters.but when i execute program and enter " asdf " after giving " as " as output it executes "df" command. i want to know why it doesn't give segmentation fault when we assign more than 2 char to a string of size 2.and why is it executing rest(after 2 char)of input as command instead of giving it as output only? also reading man page of read() i found read() should give EFAULT error,but it doesn't. I am using linux.

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  • Error compiling GLib in Ubuntu 14.04 (trying to install GimpShop)

    - by Nicolás Salvarrey
    I'm kinda new in Linux, so please take it easy on the most complicated stuff. I'm trying to install GimpShop. Installation guide asks me to install GLib first, and when I try to compile it using the make command I get errors. When I run the ./configure --prefix=/usr command, I get this: checking for a BSD-compatible install... /usr/bin/install -c checking whether build environment is sane... yes checking for gawk... no checking for mawk... mawk checking whether make sets $(MAKE)... yes checking whether to enable maintainer-specific portions of Makefiles... no checking build system type... x86_64-unknown-linux-gnu checking host system type... x86_64-unknown-linux-gnu checking for the BeOS... no checking for Win32... no checking whether to enable garbage collector friendliness... no checking whether to disable memory pools... no checking for gcc... gcc checking for C compiler default output file name... a.out checking whether the C compiler works... yes checking whether we are cross compiling... no checking for suffix of executables... checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether gcc accepts -g... yes checking for gcc option to accept ANSI C... none needed checking for style of include used by make... GNU checking dependency style of gcc... gcc3 checking for c++... no checking for g++... no checking for gcc... gcc checking whether we are using the GNU C++ compiler... no checking whether gcc accepts -g... no checking dependency style of gcc... gcc3 checking for gcc option to accept ANSI C... none needed checking for a BSD-compatible install... /usr/bin/install -c checking for special C compiler options needed for large files... no checking for _FILE_OFFSET_BITS value needed for large files... no checking for _LARGE_FILES value needed for large files... no checking for pkg-config... /usr/bin/pkg-config checking for gawk... (cached) mawk checking for perl5... no checking for perl... perl checking for indent... no checking for perl... /usr/bin/perl checking for iconv_open... yes checking how to run the C preprocessor... gcc -E checking for egrep... grep -E checking for ANSI C header files... yes checking for sys/types.h... yes checking for sys/stat.h... yes checking for stdlib.h... yes checking for string.h... yes checking for memory.h... yes checking for strings.h... yes checking for inttypes.h... yes checking for stdint.h... yes checking for unistd.h... yes checking locale.h usability... yes checking locale.h presence... yes checking for locale.h... yes checking for LC_MESSAGES... yes checking libintl.h usability... yes checking libintl.h presence... yes checking for libintl.h... yes checking for ngettext in libc... yes checking for dgettext in libc... yes checking for bind_textdomain_codeset... yes checking for msgfmt... /usr/bin/msgfmt checking for dcgettext... yes checking for gmsgfmt... /usr/bin/msgfmt checking for xgettext... /usr/bin/xgettext checking for catalogs to be installed... am ar az be bg bn bs ca cs cy da de el en_CA en_GB eo es et eu fa fi fr ga gl gu he hi hr id is it ja ko lt lv mk mn ms nb ne nl nn no or pa pl pt pt_BR ro ru sk sl sq sr sr@ije sr@Latn sv ta tl tr uk vi wa xh yi zh_CN zh_TW checking for a sed that does not truncate output... /bin/sed checking for ld used by gcc... /usr/bin/ld checking if the linker (/usr/bin/ld) is GNU ld... yes checking for /usr/bin/ld option to reload object files... -r checking for BSD-compatible nm... /usr/bin/nm -B checking whether ln -s works... yes checking how to recognise dependent libraries... pass_all checking dlfcn.h usability... yes checking dlfcn.h presence... yes checking for dlfcn.h... yes checking for g77... no checking for f77... no checking for xlf... no checking for frt... no checking for pgf77... no checking for fort77... no checking for fl32... no checking for af77... no checking for f90... no checking for xlf90... no checking for pgf90... no checking for epcf90... no checking for f95... no checking for fort... no checking for xlf95... no checking for ifc... no checking for efc... no checking for pgf95... no checking for lf95... no checking for gfortran... no checking whether we are using the GNU Fortran 77 compiler... no checking whether accepts -g... no checking the maximum length of command line arguments... 32768 checking command to parse /usr/bin/nm -B output from gcc object... ok checking for objdir... .libs checking for ar... ar checking for ranlib... ranlib checking for strip... strip checking if gcc static flag works... yes checking if gcc supports -fno-rtti -fno-exceptions... no checking for gcc option to produce PIC... -fPIC checking if gcc PIC flag -fPIC works... yes checking if gcc supports -c -o file.o... yes checking whether the gcc linker (/usr/bin/ld -m elf_x86_64) supports shared libraries... yes checking whether -lc should be explicitly linked in... no checking dynamic linker characteristics... GNU/Linux ld.so checking how to hardcode library paths into programs... immediate checking whether stripping libraries is possible... yes checking if libtool supports shared libraries... yes checking whether to build shared libraries... yes checking whether to build static libraries... no configure: creating libtool appending configuration tag "CXX" to libtool appending configuration tag "F77" to libtool checking for extra flags to get ANSI library prototypes... none needed checking for extra flags for POSIX compliance... none needed checking for ANSI C header files... (cached) yes checking for vprintf... yes checking for _doprnt... no checking for working alloca.h... yes checking for alloca... yes checking for atexit... yes checking for on_exit... yes checking for char... yes checking size of char... 1 checking for short... yes checking size of short... 2 checking for long... yes checking size of long... 8 checking for int... yes checking size of int... 4 checking for void *... yes checking size of void *... 8 checking for long long... yes checking size of long long... 8 checking for __int64... no checking size of __int64... 0 checking for format to printf and scanf a guint64... %llu checking for an ANSI C-conforming const... yes checking if malloc() and friends prototypes are gmem.h compatible... no checking for growing stack pointer... yes checking for __inline... yes checking for __inline__... yes checking for inline... yes checking if inline functions in headers work... yes checking for ISO C99 varargs macros in C... yes checking for ISO C99 varargs macros in C++... no checking for GNUC varargs macros... yes checking for GNUC visibility attribute... yes checking whether byte ordering is bigendian... no checking dirent.h usability... yes checking dirent.h presence... yes checking for dirent.h... yes checking float.h usability... yes checking float.h presence... yes checking for float.h... yes checking limits.h usability... yes checking limits.h presence... yes checking for limits.h... yes checking pwd.h usability... yes checking pwd.h presence... yes checking for pwd.h... yes checking sys/param.h usability... yes checking sys/param.h presence... yes checking for sys/param.h... yes checking sys/poll.h usability... yes checking sys/poll.h presence... yes checking for sys/poll.h... yes checking sys/select.h usability... yes checking sys/select.h presence... yes checking for sys/select.h... yes checking for sys/types.h... (cached) yes checking sys/time.h usability... yes checking sys/time.h presence... yes checking for sys/time.h... yes checking sys/times.h usability... yes checking sys/times.h presence... yes checking for sys/times.h... yes checking for unistd.h... (cached) yes checking values.h usability... yes checking values.h presence... yes checking for values.h... yes checking for stdint.h... (cached) yes checking sched.h usability... yes checking sched.h presence... yes checking for sched.h... yes checking langinfo.h usability... yes checking langinfo.h presence... yes checking for langinfo.h... yes checking for nl_langinfo... yes checking for nl_langinfo and CODESET... yes checking whether we are using the GNU C Library 2.1 or newer... yes checking stddef.h usability... yes checking stddef.h presence... yes checking for stddef.h... yes checking for stdlib.h... (cached) yes checking for string.h... (cached) yes checking for setlocale... yes checking for size_t... yes checking size of size_t... 8 checking for the appropriate definition for size_t... unsigned long checking for lstat... yes checking for strerror... yes checking for strsignal... yes checking for memmove... yes checking for mkstemp... yes checking for vsnprintf... yes checking for stpcpy... yes checking for strcasecmp... yes checking for strncasecmp... yes checking for poll... yes checking for getcwd... yes checking for nanosleep... yes checking for vasprintf... yes checking for setenv... yes checking for unsetenv... yes checking for getc_unlocked... yes checking for readlink... yes checking for symlink... yes checking for C99 vsnprintf... yes checking whether printf supports positional parameters... yes checking for signed... yes checking for long long... (cached) yes checking for long double... yes checking for wchar_t... yes checking for wint_t... yes checking for size_t... (cached) yes checking for ptrdiff_t... yes checking for inttypes.h... yes checking for stdint.h... yes checking for snprintf... yes checking for C99 snprintf... yes checking for sys_errlist... yes checking for sys_siglist... yes checking for sys_siglist declaration... yes checking for fd_set... yes, found in sys/types.h checking whether realloc (NULL,) will work... yes checking for nl_langinfo (CODESET)... yes checking for OpenBSD strlcpy/strlcat... no checking for an implementation of va_copy()... yes checking for an implementation of __va_copy()... yes checking whether va_lists can be copied by value... no checking for dlopen... no checking for NSLinkModule... no checking for dlopen in -ldl... yes checking for dlsym in -ldl... yes checking for RTLD_GLOBAL brokenness... no checking for preceeding underscore in symbols... no checking for dlerror... yes checking for the suffix of shared libraries... .so checking for gspawn implementation... gspawn.lo checking for GIOChannel implementation... giounix.lo checking for platform-dependent source... checking whether to compile timeloop... yes checking if building for some Win32 platform... no checking for thread implementation... posix checking thread related cflags... -pthread checking for sched_get_priority_min... yes checking thread related libraries... -pthread checking for localtime_r... yes checking for posix getpwuid_r... yes checking size of pthread_t... 8 checking for pthread_attr_setstacksize... yes checking for minimal/maximal thread priority... sched_get_priority_min(SCHED_OTHER)/sched_get_priority_max(SCHED_OTHER) checking for pthread_setschedparam... yes checking for posix yield function... sched_yield checking size of pthread_mutex_t... 40 checking byte contents of PTHREAD_MUTEX_INITIALIZER... 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 checking whether to use assembler code for atomic operations... x86_64 checking value of POLLIN... 1 checking value of POLLOUT... 4 checking value of POLLPRI... 2 checking value of POLLERR... 8 checking value of POLLHUP... 16 checking value of POLLNVAL... 32 checking for EILSEQ... yes configure: creating ./config.status config.status: creating glib-2.0.pc config.status: creating glib-2.0-uninstalled.pc config.status: creating gmodule-2.0.pc config.status: creating gmodule-no-export-2.0.pc config.status: creating gmodule-2.0-uninstalled.pc config.status: creating gthread-2.0.pc config.status: creating gthread-2.0-uninstalled.pc config.status: creating gobject-2.0.pc config.status: creating gobject-2.0-uninstalled.pc config.status: creating glib-zip config.status: creating glib-gettextize config.status: creating Makefile config.status: creating build/Makefile config.status: creating build/win32/Makefile config.status: creating build/win32/dirent/Makefile config.status: creating glib/Makefile config.status: creating glib/libcharset/Makefile config.status: creating glib/gnulib/Makefile config.status: creating gmodule/Makefile config.status: creating gmodule/gmoduleconf.h config.status: creating gobject/Makefile config.status: creating gobject/glib-mkenums config.status: creating gthread/Makefile config.status: creating po/Makefile.in config.status: creating docs/Makefile config.status: creating docs/reference/Makefile config.status: creating docs/reference/glib/Makefile config.status: creating docs/reference/glib/version.xml config.status: creating docs/reference/gobject/Makefile config.status: creating docs/reference/gobject/version.xml config.status: creating tests/Makefile config.status: creating tests/gobject/Makefile config.status: creating m4macros/Makefile config.status: creating config.h config.status: config.h is unchanged config.status: executing depfiles commands config.status: executing default-1 commands config.status: executing glibconfig.h commands config.status: glibconfig.h is unchanged config.status: executing chmod-scripts commands nsalvarrey@Delleuze:~/glib-2.6.3$ ^C nsalvarrey@Delleuze:~/glib-2.6.3$ And then, with the make command, I get this: galias.h:83:39: error: 'g_ascii_digit_value' aliased to undefined symbol 'IA__g_ascii_digit_value' extern __typeof (g_ascii_digit_value) g_ascii_digit_value __attribute((alias("IA__g_ascii_digit_value"), visibility("default"))); ^ In file included from garray.c:35:0: galias.h:31:35: error: 'g_allocator_new' aliased to undefined symbol 'IA__g_allocator_new' extern __typeof (g_allocator_new) g_allocator_new __attribute((alias("IA__g_allocator_new"), visibility("default"))); ^ make[4]: *** [garray.lo] Error 1 make[4]: se sale del directorio «/home/nsalvarrey/glib-2.6.3/glib» make[3]: *** [all-recursive] Error 1 make[3]: se sale del directorio «/home/nsalvarrey/glib-2.6.3/glib» make[2]: *** [all] Error 2 make[2]: se sale del directorio «/home/nsalvarrey/glib-2.6.3/glib» make[1]: *** [all-recursive] Error 1 make[1]: se sale del directorio «/home/nsalvarrey/glib-2.6.3» make: *** [all] Error 2 nsalvarrey@Delleuze:~/glib-2.6.3$ (it's actually a lot longer) Can somebody help me?

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  • Problems installing clamcour

    - by user10778
    Hello People, when i try to install clamcour from terminal, it gives me this error, somebody can help me? calmcourdir# ./configure checking for libraries containing socket functions... -lc checking for socket... yes checking for bind... yes checking for listen... yes checking for accept... yes checking for shutdown... yes checking for socklen_t... yes checking for struct sockaddr_un.sun_len... no System log functions checking syslog.h usability... yes checking syslog.h presence... yes checking for syslog.h... yes checking for openlog... yes checking for syslog... yes checking for closelog... yes Time functions checking whether time.h and sys/time.h may both be included... yes checking whether struct tm is in sys/time.h or time.h... time.h checking for localtime_r... yes checking for strftime... yes checking for unistd.h... (cached) yes checking limits.h usability... yes checking limits.h presence... yes checking for limits.h... yes checking for sysconf... yes BZip2 support checking bzlib.h usability... no checking bzlib.h presence... no checking for bzlib.h... no checking for BZ2_bzWriteOpen in -lbz2... no GZip support checking zlib.h usability... no checking zlib.h presence... no checking for zlib.h... no checking for gzopen in -lz... no LibClamAV support checking for /usr/bin/clamav-config... no checking for /usr/local/bin/courier-config... no checking for /usr/clamav/bin/clamav-config... no checking for /usr/local/clamav/bin/clamav-config... no ./configure: line 25234: : command not found configure: error: Cannot find clamav-config

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  • Problems building clamcour

    - by user10778
    Hello People, when i try to install clamcour from terminal, it gives me this error, somebody can help me? calmcourdir# ./configure checking for libraries containing socket functions... -lc checking for socket... yes checking for bind... yes checking for listen... yes checking for accept... yes checking for shutdown... yes checking for socklen_t... yes checking for struct sockaddr_un.sun_len... no System log functions checking syslog.h usability... yes checking syslog.h presence... yes checking for syslog.h... yes checking for openlog... yes checking for syslog... yes checking for closelog... yes Time functions checking whether time.h and sys/time.h may both be included... yes checking whether struct tm is in sys/time.h or time.h... time.h checking for localtime_r... yes checking for strftime... yes checking for unistd.h... (cached) yes checking limits.h usability... yes checking limits.h presence... yes checking for limits.h... yes checking for sysconf... yes BZip2 support checking bzlib.h usability... no checking bzlib.h presence... no checking for bzlib.h... no checking for BZ2_bzWriteOpen in -lbz2... no GZip support checking zlib.h usability... no checking zlib.h presence... no checking for zlib.h... no checking for gzopen in -lz... no LibClamAV support checking for /usr/bin/clamav-config... no checking for /usr/local/bin/courier-config... no checking for /usr/clamav/bin/clamav-config... no checking for /usr/local/clamav/bin/clamav-config... no ./configure: line 25234: : command not found configure: error: Cannot find clamav-config

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  • Write and fprintf for file I/O

    - by Darryl Gove
    fprintf() does buffered I/O, where as write() does unbuffered I/O. So once the write() completes, the data is in the file, whereas, for fprintf() it may take a while for the file to get updated to reflect the output. This results in a significant performance difference - the write works at disk speed. The following is a program to test this: #include <fcntl.h #include <unistd.h #include <stdio.h #include <stdlib.h #include <errno.h #include <stdio.h #include <sys/time.h #include <sys/types.h #include <sys/stat.h static double s_time; void starttime() { s_time=1.0*gethrtime(); } void endtime(long its) { double e_time=1.0*gethrtime(); printf("Time per iteration %5.2f MB/s\n", (1.0*its)/(e_time-s_time*1.0)*1000); s_time=1.0*gethrtime(); } #define SIZE 10*1024*1024 void test_write() { starttime(); int file = open("./test.dat",O_WRONLY|O_CREAT,S_IWGRP|S_IWOTH|S_IWUSR); for (int i=0; i<SIZE; i++) { write(file,"a",1); } close(file); endtime(SIZE); } void test_fprintf() { starttime(); FILE* file = fopen("./test.dat","w"); for (int i=0; i<SIZE; i++) { fprintf(file,"a"); } fclose(file); endtime(SIZE); } void test_flush() { starttime(); FILE* file = fopen("./test.dat","w"); for (int i=0; i<SIZE; i++) { fprintf(file,"a"); fflush(file); } fclose(file); endtime(SIZE); } int main() { test_write(); test_fprintf(); test_flush(); } Compiling and running I get 0.2MB/s for write() and 6MB/s for fprintf(). A large difference. There's three tests in this example, the third test uses fprintf() and fflush(). This is equivalent to write() both in performance and in functionality. Which leads to the suggestion that fprintf() (and other buffering I/O functions) are the fastest way of writing to files, and that fflush() should be used to enforce synchronisation of the file contents.

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  • Linux Scheduler (not using all cores on multi-core machine) RHEL6

    - by User512
    I'm seeing strange behavior on one of my servers (running RHEL 6). There seems to be something wrong with the scheduler. Here's the test program I'm using: #include <stdio.h> #include <unistd.h> #include <stdlib.h> void RunClient(int i) { printf("Starting client %d\n", i); while (true) { } } int main(int argc, char** argv) { for (int i = 0; i < 4; ++i) { pid_t p_id = fork(); if (p_id == -1) { perror("fork"); } else if (p_id == 0) { RunClient(i); exit(0); } } return 0; } This machine has a lot more than 4 cores so we'd expect all processes to be running at 100%. When I check on top, the cpu usage varies. Sometimes it's split (100%, 33%, 33%, 33%), other times it's split (100%, 100%, 50%, 50%). When I try this test on another server of ours (running RHEL 5), there are no issues (it's 100%, 100%, 100%, 100%) as expected. What's causing this and how can I fix it? Thanks

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  • Installing checkinstall on x86_64 bit

    - by SephMerah
    I downloaded the source for check install. checkinstall-1.6.2.tar.gz. I then tar -xzvf checkinstall-1.6.2.tar.gz Then I make. It prints this error: [root@ip-50-63-180-135 checkinstall-1.6.2]# make for file in locale/checkinstall-*.po ; do \ case ${file} in \ locale/checkinstall-template.po) ;; \ *) \ out=`echo $file | sed -s 's/po/mo/'` ; \ msgfmt -o ${out} ${file} ; \ if [ $? != 0 ] ; then \ exit 1 ; \ fi ; \ ;; \ esac ; \ done make -C installwatch make[1]: Entering directory `/home/sofiane/checkinstall-1.6.2/installwatch' gcc -Wall -c -D_GNU_SOURCE -DPIC -fPIC -D_REENTRANT -DVERSION=\"0.7.0beta7\" installwatch.c installwatch.c:2942: error: conflicting types for 'readlink' /usr/include/unistd.h:828: note: previous declaration of 'readlink' was here installwatch.c:3080: error: conflicting types for 'scandir' /usr/include/dirent.h:252: note: previous declaration of 'scandir' was here installwatch.c:3692: error: conflicting types for 'scandir64' /usr/include/dirent.h:275: note: previous declaration of 'scandir64' was here make[1]: *** [installwatch.o] Error 1 make[1]: Leaving directory `/home/sofiane/checkinstall-1.6.2/installwatch' make: *** [all] Error 2 I searched extensively on this issue and this solution looks promising. Should I attempt to install checkinstall as an fpm? What would be the best way to go about that? Centos 6.3 x86_64

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  • Can't seem to get C TCP Server-Client Communications Right

    - by Zeesponge
    Ok i need some serious help here. I have to make a TCP Server Client. When the Client connects to server using a three stage handshake. AFterwards... while the Client is running in the terminal, the user enters linux shell commands like xinput list, ls -1, ect... something that uses standard output. The server accepts the commands and uses system() (in a fork() in an infinite loop) to run the commands and the standard output is redirected to the client, where the client prints out each line. Afterward the server sends a completion signal of "\377\n". In which the client goes back to the command prompt asking for a new command and closes its connection and exit()'s when inputting "quit". I know that you have to dup2() both the STDOUT_FILENO and STDERR_FILENO to the clients file descriptor {dup2(client_FD, STDOUT_FILENO). Everything works accept when it comes for the client to retrieve system()'s stdout and printing it out... all i get is a blank line with a blinking cursor (client waiting on stdin). I tried all kinds of different routes with no avail... If anyone can help out i would greatly appreciate it TCP SERVER CODE include #include <sys/socket.h> #include <stdio.h> #include <string.h> #include <netinet/in.h> #include <signal.h> #include <unistd.h> #include <stdlib.h> #include <errno.h> //Prototype void handle_client(int connect_fd); int main() { int server_sockfd, client_sockfd; socklen_t server_len, client_len; struct sockaddr_in server_address; struct sockaddr_in client_address; server_sockfd = socket(AF_INET, SOCK_STREAM, 0); server_address.sin_family = AF_INET; server_address.sin_addr.s_addr = htonl(INADDR_ANY); server_address.sin_port = htons(9734); server_len = sizeof(server_address); bind(server_sockfd, (struct sockaddr *)&server_address, server_len); /* Create a connection queue, ignore child exit details and wait for clients. */ listen(server_sockfd, 10); signal(SIGCHLD, SIG_IGN); while(1) { printf("server waiting\n"); client_len = sizeof(client_address); client_sockfd = accept(server_sockfd, (struct sockaddr *)&client_address, &client_len); if(fork() == 0) handle_client(client_sockfd); else close(client_sockfd); } } void handle_client(int connect_fd) { const char* remsh = "<remsh>\n"; const char* ready = "<ready>\n"; const char* ok = "<ok>\n"; const char* command = "<command>\n"; const char* complete = "<\377\n"; const char* shared_secret = "<shapoopi>\n"; static char server_msg[201]; static char client_msg[201]; static char commands[201]; int sys_return; //memset client_msg, server_msg, commands memset(&client_msg, 0, sizeof(client_msg)); memset(&server_msg, 0, sizeof(client_msg)); memset(&commands, 0, sizeof(commands)); //read remsh from client read(connect_fd, &client_msg, 200); //check remsh validity from client if(strcmp(client_msg, remsh) != 0) { errno++; perror("Error Establishing Handshake"); close(connect_fd); exit(1); } //memset client_msg memset(&client_msg, 0, sizeof(client_msg)); //write remsh to client write(connect_fd, remsh, strlen(remsh)); //read shared_secret from client read(connect_fd, &client_msg, 200); //check shared_secret validity from client if(strcmp(client_msg, shared_secret) != 0) { errno++; perror("Invalid Security Passphrase"); write(connect_fd, "no", 2); close(connect_fd); exit(1); } //memset client_msg memset(&client_msg, 0, sizeof(client_msg)); //write ok to client write(connect_fd, ok, strlen(ok)); // dup2 STDOUT_FILENO <= client fd, STDERR_FILENO <= client fd dup2(connect_fd, STDOUT_FILENO); dup2(connect_fd, STDERR_FILENO); //begin while... while read (client_msg) from server and >0 while(read(connect_fd, &client_msg, 200) > 0) { //check command validity from client if(strcmp(client_msg, command) != 0) { errno++; perror("Error, unable to retrieve data"); close(connect_fd); exit(1); } //memset client_msg memset(&client_msg, 0, sizeof(client_msg)); //write ready to client write(connect_fd, ready, strlen(ready)); //read commands from client read(connect_fd, &commands, 200); //run commands using system( ) sys_return = system(commands); //check success of system( ) if(sys_return < 0) { perror("Invalid Commands"); errno++; } //memset commands memset(commands, 0, sizeof(commands)); //write complete to client write(connect_fd, complete, sizeof(complete)); } } TCP CLIENT CODE #include <sys/types.h> #include <sys/socket.h> #include <stdio.h> #include <string.h> #include <netinet/in.h> #include <arpa/inet.h> #include <unistd.h> #include <stdlib.h> #include <errno.h> #include "readline.c" int main(int argc, char *argv[]) { int sockfd; int len; struct sockaddr_in address; int result; const char* remsh = "<remsh>\n"; const char* ready = "<ready>\n"; const char* ok = "<ok>\n"; const char* command = "<command>\n"; const char* complete = "<\377\n"; const char* shared_secret = "<shapoopi>\n"; static char server_msg[201]; static char client_msg[201]; memset(&client_msg, 0, sizeof(client_msg)); memset(&server_msg, 0, sizeof(server_msg)); /* Create a socket for the client. */ sockfd = socket(AF_INET, SOCK_STREAM, 0); /* Name the socket, as agreed with the server. */ memset(&address, 0, sizeof(address)); address.sin_family = AF_INET; address.sin_addr.s_addr = inet_addr(argv[1]); address.sin_port = htons(9734); len = sizeof(address); /* Now connect our socket to the server's socket. */ result = connect(sockfd, (struct sockaddr *)&address, len); if(result == -1) { perror("ACCESS DENIED"); exit(1); } //write remsh to server write(sockfd, remsh, strlen(remsh)); //read remsh from server read(sockfd, &server_msg, 200); //check remsh validity from server if(strcmp(server_msg, remsh) != 0) { errno++; perror("Error Establishing Initial Handshake"); close(sockfd); exit(1); } //memset server_msg memset(&server_msg, 0, sizeof(server_msg)); //write shared secret text to server write(sockfd, shared_secret, strlen(shared_secret)); //read ok from server read(sockfd, &server_msg, 200); //check ok velidity from server if(strcmp(server_msg, ok) != 0 ) { errno++; perror("Incorrect security phrase"); close(sockfd); exit(1); } //? dup2 STDIN_FILENO = server socket fd? //dup2(sockfd, STDIN_FILENO); //begin while(1)/////////////////////////////////////// while(1){ //memset both msg arrays memset(&client_msg, 0, sizeof(client_msg)); memset(&server_msg, 0, sizeof(server_msg)); //print Enter Command, scan input, fflush to stdout printf("<<Enter Command>> "); scanf("%s", client_msg); fflush(stdout); //check quit input, if true close and exit successfully if(strcmp(client_msg, "quit") == 0) { printf("Exiting\n"); close(sockfd); exit(EXIT_SUCCESS); } //write command to server write(sockfd, command, strlen(command)); //read ready from server read(sockfd, &server_msg, 200); //check ready validity from server if(strcmp(server_msg, ready) != 0) { errno++; perror("Failed Server Communications"); close(sockfd); exit(1); } //memset server_msg memset(&server_msg, 0, sizeof(server_msg)); //begin looping and retrieving from stdin, //break loop at EOF or complete while((read(sockfd, server_msg, 200) != 0) && (strcmp(server_msg, complete) != 0)) { //while((fgets(server_msg, 4096, stdin) != EOF) || (strcmp(server_msg, complete) == 0)) { printf("%s", server_msg); memset(&server_msg, 0, sizeof(server_msg)); } } }

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  • C sockets, chat server and client, problem echoing back.

    - by wretrOvian
    Hi This is my chat server : #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netdb.h> #include <string.h> #define LISTEN_Q 20 #define MSG_SIZE 1024 struct userlist { int sockfd; struct sockaddr addr; struct userlist *next; }; int main(int argc, char *argv[]) { // declare. int listFD, newFD, fdmax, i, j, bytesrecvd; char msg[MSG_SIZE], ipv4[INET_ADDRSTRLEN]; struct addrinfo hints, *srvrAI; struct sockaddr_storage newAddr; struct userlist *users, *uptr, *utemp; socklen_t newAddrLen; fd_set master_set, read_set; // clear sets FD_ZERO(&master_set); FD_ZERO(&read_set); // create a user list users = (struct userlist *)malloc(sizeof(struct userlist)); users->sockfd = -1; //users->addr = NULL; users->next = NULL; // clear hints memset(&hints, 0, sizeof hints); // prep hints hints.ai_family = AF_INET; hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; // get srver info if(getaddrinfo("localhost", argv[1], &hints, &srvrAI) != 0) { perror("* ERROR | getaddrinfo()\n"); exit(1); } // get a socket if((listFD = socket(srvrAI->ai_family, srvrAI->ai_socktype, srvrAI->ai_protocol)) == -1) { perror("* ERROR | socket()\n"); exit(1); } // bind socket bind(listFD, srvrAI->ai_addr, srvrAI->ai_addrlen); // listen on socket if(listen(listFD, LISTEN_Q) == -1) { perror("* ERROR | listen()\n"); exit(1); } // add listfd to master_set FD_SET(listFD, &master_set); // initialize fdmax fdmax = listFD; while(1) { // equate read_set = master_set; // run select if(select(fdmax+1, &read_set, NULL, NULL, NULL) == -1) { perror("* ERROR | select()\n"); exit(1); } // query all sockets for(i = 0; i <= fdmax; i++) { if(FD_ISSET(i, &read_set)) { // found active sockfd if(i == listFD) { // new connection // accept newAddrLen = sizeof newAddr; if((newFD = accept(listFD, (struct sockaddr *)&newAddr, &newAddrLen)) == -1) { perror("* ERROR | select()\n"); exit(1); } // resolve ip if(inet_ntop(AF_INET, &(((struct sockaddr_in *)&newAddr)->sin_addr), ipv4, INET_ADDRSTRLEN) == -1) { perror("* ERROR | inet_ntop()"); exit(1); } fprintf(stdout, "* Client Connected | %s\n", ipv4); // add to master list FD_SET(newFD, &master_set); // create new userlist component utemp = (struct userlist*)malloc(sizeof(struct userlist)); utemp->next = NULL; utemp->sockfd = newFD; utemp->addr = *((struct sockaddr *)&newAddr); // iterate to last node for(uptr = users; uptr->next != NULL; uptr = uptr->next) { } // add uptr->next = utemp; // update fdmax if(newFD > fdmax) fdmax = newFD; } else { // existing sockfd transmitting data // read if((bytesrecvd = recv(i, msg, MSG_SIZE, 0)) == -1) { perror("* ERROR | recv()\n"); exit(1); } msg[bytesrecvd] = '\0'; // find out who sent? for(uptr = users; uptr->next != NULL; uptr = uptr->next) { if(i == uptr->sockfd) break; } // resolve ip if(inet_ntop(AF_INET, &(((struct sockaddr_in *)&(uptr->addr))->sin_addr), ipv4, INET_ADDRSTRLEN) == -1) { perror("* ERROR | inet_ntop()"); exit(1); } // print fprintf(stdout, "%s\n", msg); // send to all for(j = 0; j <= fdmax; j++) { if(FD_ISSET(j, &master_set)) { if(send(j, msg, strlen(msg), 0) == -1) perror("* ERROR | send()"); } } } // handle read from client } // end select result handle } // end looping fds } // end while return 0; } This is my client: #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netdb.h> #include <string.h> #define MSG_SIZE 1024 int main(int argc, char *argv[]) { // declare. int newFD, bytesrecvd, fdmax; char msg[MSG_SIZE]; fd_set master_set, read_set; struct addrinfo hints, *srvrAI; // clear sets FD_ZERO(&master_set); FD_ZERO(&read_set); // clear hints memset(&hints, 0, sizeof hints); // prep hints hints.ai_family = AF_INET; hints.ai_socktype = SOCK_STREAM; hints.ai_flags = AI_PASSIVE; // get srver info if(getaddrinfo(argv[1], argv[2], &hints, &srvrAI) != 0) { perror("* ERROR | getaddrinfo()\n"); exit(1); } // get a socket if((newFD = socket(srvrAI->ai_family, srvrAI->ai_socktype, srvrAI->ai_protocol)) == -1) { perror("* ERROR | socket()\n"); exit(1); } // connect to server if(connect(newFD, srvrAI->ai_addr, srvrAI->ai_addrlen) == -1) { perror("* ERROR | connect()\n"); exit(1); } // add to master, and add keyboard FD_SET(newFD, &master_set); FD_SET(STDIN_FILENO, &master_set); // initialize fdmax if(newFD > STDIN_FILENO) fdmax = newFD; else fdmax = STDIN_FILENO; while(1) { // equate read_set = master_set; if(select(fdmax+1, &read_set, NULL, NULL, NULL) == -1) { perror("* ERROR | select()"); exit(1); } // check server if(FD_ISSET(newFD, &read_set)) { // read data if((bytesrecvd = recv(newFD, msg, MSG_SIZE, 0)) < 0 ) { perror("* ERROR | recv()"); exit(1); } msg[bytesrecvd] = '\0'; // print fprintf(stdout, "%s\n", msg); } // check keyboard if(FD_ISSET(STDIN_FILENO, &read_set)) { // read data from stdin if((bytesrecvd = read(STDIN_FILENO, msg, MSG_SIZE)) < 0) { perror("* ERROR | read()"); exit(1); } msg[bytesrecvd] = '\0'; // send if((send(newFD, msg, bytesrecvd, 0)) == -1) { perror("* ERROR | send()"); exit(1); } } } return 0; } The problem is with the part where the server recv()s data from an FD, then tries echoing back to all [send() ]; it just dies, w/o errors, and my client is left looping :(

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  • Microbenchmark showing process-switching faster than thread-switching; what's wrong?

    - by Yang
    I have two simple microbenchmarks trying to measure thread- and process-switching overheads, but the process-switching overhead. The code is living here, and r1667 is pasted below: https://assorted.svn.sourceforge.net/svnroot/assorted/sandbox/trunk/src/c/process_switch_bench.c // on zs, ~2.1-2.4us/switch #include <stdlib.h> #include <fcntl.h> #include <stdint.h> #include <stdio.h> #include <semaphore.h> #include <unistd.h> #include <sys/wait.h> #include <sys/types.h> #include <sys/time.h> #include <pthread.h> uint32_t COUNTER; pthread_mutex_t LOCK; pthread_mutex_t START; sem_t *s0, *s1, *s2; void * threads ( void * unused ) { // Wait till we may fire away sem_wait(s2); for (;;) { pthread_mutex_lock(&LOCK); pthread_mutex_unlock(&LOCK); COUNTER++; sem_post(s0); sem_wait(s1); } return 0; } int64_t timeInMS () { struct timeval t; gettimeofday(&t, NULL); return ( (int64_t)t.tv_sec * 1000 + (int64_t)t.tv_usec / 1000 ); } int main ( int argc, char ** argv ) { int64_t start; pthread_t t1; pthread_mutex_init(&LOCK, NULL); COUNTER = 0; s0 = sem_open("/s0", O_CREAT, 0022, 0); if (s0 == 0) { perror("sem_open"); exit(1); } s1 = sem_open("/s1", O_CREAT, 0022, 0); if (s1 == 0) { perror("sem_open"); exit(1); } s2 = sem_open("/s2", O_CREAT, 0022, 0); if (s2 == 0) { perror("sem_open"); exit(1); } int x, y, z; sem_getvalue(s0, &x); sem_getvalue(s1, &y); sem_getvalue(s2, &z); printf("%d %d %d\n", x, y, z); pid_t pid = fork(); if (pid) { pthread_create(&t1, NULL, threads, NULL); pthread_detach(t1); // Get start time and fire away start = timeInMS(); sem_post(s2); sem_post(s2); // Wait for about a second sleep(1); // Stop thread pthread_mutex_lock(&LOCK); // Find out how much time has really passed. sleep won't guarantee me that // I sleep exactly one second, I might sleep longer since even after being // woken up, it can take some time before I gain back CPU time. Further // some more time might have passed before I obtained the lock! int64_t time = timeInMS() - start; // Correct the number of thread switches accordingly COUNTER = (uint32_t)(((uint64_t)COUNTER * 2 * 1000) / time); printf("Number of process switches in about one second was %u\n", COUNTER); printf("roughly %f microseconds per switch\n", 1000000.0 / COUNTER); // clean up kill(pid, 9); wait(0); sem_close(s0); sem_close(s1); sem_unlink("/s0"); sem_unlink("/s1"); sem_unlink("/s2"); } else { if (1) { sem_t *t = s0; s0 = s1; s1 = t; } threads(0); // never return } return 0; } https://assorted.svn.sourceforge.net/svnroot/assorted/sandbox/trunk/src/c/thread_switch_bench.c // From <http://stackoverflow.com/questions/304752/how-to-estimate-the-thread-context-switching-overhead> // on zs, ~4-5us/switch; tried making COUNTER updated only by one thread, but no difference #include <stdlib.h> #include <stdint.h> #include <stdio.h> #include <pthread.h> #include <unistd.h> #include <sys/time.h> uint32_t COUNTER; pthread_mutex_t LOCK; pthread_mutex_t START; pthread_cond_t CONDITION; void * threads ( void * unused ) { // Wait till we may fire away pthread_mutex_lock(&START); pthread_mutex_unlock(&START); int first=1; pthread_mutex_lock(&LOCK); // If I'm not the first thread, the other thread is already waiting on // the condition, thus Ihave to wake it up first, otherwise we'll deadlock if (COUNTER > 0) { pthread_cond_signal(&CONDITION); first=0; } for (;;) { if (first) COUNTER++; pthread_cond_wait(&CONDITION, &LOCK); // Always wake up the other thread before processing. The other // thread will not be able to do anything as long as I don't go // back to sleep first. pthread_cond_signal(&CONDITION); } pthread_mutex_unlock(&LOCK); return 0; } int64_t timeInMS () { struct timeval t; gettimeofday(&t, NULL); return ( (int64_t)t.tv_sec * 1000 + (int64_t)t.tv_usec / 1000 ); } int main ( int argc, char ** argv ) { int64_t start; pthread_t t1; pthread_t t2; pthread_mutex_init(&LOCK, NULL); pthread_mutex_init(&START, NULL); pthread_cond_init(&CONDITION, NULL); pthread_mutex_lock(&START); COUNTER = 0; pthread_create(&t1, NULL, threads, NULL); pthread_create(&t2, NULL, threads, NULL); pthread_detach(t1); pthread_detach(t2); // Get start time and fire away start = timeInMS(); pthread_mutex_unlock(&START); // Wait for about a second sleep(1); // Stop both threads pthread_mutex_lock(&LOCK); // Find out how much time has really passed. sleep won't guarantee me that // I sleep exactly one second, I might sleep longer since even after being // woken up, it can take some time before I gain back CPU time. Further // some more time might have passed before I obtained the lock! int64_t time = timeInMS() - start; // Correct the number of thread switches accordingly COUNTER = (uint32_t)(((uint64_t)COUNTER * 2 * 1000) / time); printf("Number of thread switches in about one second was %u\n", COUNTER); printf("roughly %f microseconds per switch\n", 1000000.0 / COUNTER); return 0; }

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  • Issue on file existence in C

    - by darkie15
    Hi All, Here is my code which checks if the file exists : #include<stdio.h> #include<zlib.h> #include<unistd.h> #include<string.h> int main(int argc, char *argv[]) { char *path=NULL; FILE *file = NULL; char *fileSeparator = "/"; size_t size=100; int index ; printf("\nArgument count is = %d", argc); if (argc <= 1) { printf("\nUsage: ./output filename1 filename2 ..."); printf("\n The program will display human readable information about the PNG file provided"); } else if (argc > 1) { for (index = 1; index < argc;index++) { path = getcwd(path, size); strcat(path, fileSeparator); printf("\n File name entered is = %s", argv[index]); strcat(path,argv[index]); printf("\n The complete path of the file name is = %s", path); if (access(path, F_OK) != -1) { printf("File does exist"); } else { printf("File does not exist"); } path=NULL; } } return 0; } On running the command ./output test.txt test2.txt The output is: $ ./output test.txt test2.txt Argument count is = 3 File name entered is = test.txt The complete path of the file name is = /home/welcomeuser/test.txt File does not exist File name entered is = test2.txt The complete path of the file name is = /home/welcomeuser/test2.txt File does not exist Now test.txt does exist on the system: $ ls assignment.c output.exe output.exe.stackdump test.txt and yet test.txt is shown as a file not existing. Please help me understand the issue here. Also, please feel free to post any suggestions to improve the code/avoid a bug. Regards, darkie

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  • Help debugging c fifos code - stack smashing detected - open call not functioning - removing pipes

    - by nunos
    I have three bugs/questions regarding the source code pasted below: stack smashing deteced: In order to compile and not have that error I have addedd the gcc compile flag -fno-stack-protector. However, this should be just a temporary solution, since I would like to find where the cause for this is and correct it. However, I haven't been able to do so. Any clues? For some reason, the last open function call doesn't work and the programs just stops there, without an error, even though the fifo already exists. I want to delete the pipes from the filesystem after before terminating the processes. I have added close and unlink statements at the end, but the fifos are not removed. What am I doing wrong? Thanks very much in advance. P.S.: I am pasting here the whole source file for additional clarity. Just ignore the comments, since they are in my own native language. server.c: #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <errno.h> #define MAX_INPUT_LENGTH 100 #define FIFO_NAME_MAX_LEN 20 #define FIFO_DIR "/tmp/" #define FIFO_NAME_CMD_CLI_TO_SRV "lrc_cmd_cli_to_srv" typedef enum { false, true } bool; bool background = false; char* logfile = NULL; void read_from_fifo(int fd, char** var) { int n_bytes; read(fd, &n_bytes, sizeof(int)); *var = (char *) malloc (n_bytes); read(fd, *var, n_bytes); printf("read %d bytes '%s'\n", n_bytes, *var); } void write_to_fifo(int fd, char* data) { int n_bytes = (strlen(data)+1) * sizeof(char); write(fd, &n_bytes, sizeof(int)); //primeiro envia o numero de bytes que a proxima instrucao write ira enviar write(fd, data, n_bytes); printf("writing %d bytes '%s'\n", n_bytes, data); } int main(int argc, char* argv[]) { //CRIA FIFO CMD_CLI_TO_SRV, se ainda nao existir char* fifo_name_cmd_cli_to_srv; fifo_name_cmd_cli_to_srv = (char*) malloc ( (strlen(FIFO_NAME_CMD_CLI_TO_SRV) + strlen(FIFO_DIR) + 1) * sizeof(char) ); strcpy(fifo_name_cmd_cli_to_srv, FIFO_DIR); strcat(fifo_name_cmd_cli_to_srv, FIFO_NAME_CMD_CLI_TO_SRV); int n = mkfifo(fifo_name_cmd_cli_to_srv, 0660); //TODO ver permissoes if (n < 0 && errno != EEXIST) //se houver erro, e nao for por causa de ja haver um com o mesmo nome, termina o programa { fprintf(stderr, "erro ao criar o fifo\n"); fprintf(stderr, "errno: %d\n", errno); exit(4); } //se por acaso já existir, nao cria o fifo e continua o programa normalmente //le informacao enviada pelo cliente, nesta ordem: //1. pid (em formato char*) do processo cliente //2. comando /CONNECT //3. nome de fifo INFO_SRV_TO_CLIXXX //4. nome de fifo MSG_SRV_TO_CLIXXX char* command; char* fifo_name_info_srv_to_cli; char* fifo_name_msg_srv_to_cli; char* client_pid_string; int client_pid; int fd_cmd_cli_to_srv, fd_info_srv_to_cli; fd_cmd_cli_to_srv = open(fifo_name_cmd_cli_to_srv, O_RDONLY); read_from_fifo(fd_cmd_cli_to_srv, &client_pid_string); client_pid = atoi(client_pid_string); read_from_fifo(fd_cmd_cli_to_srv, &command); //recebe commando /CONNECT read_from_fifo(fd_cmd_cli_to_srv, &fifo_name_info_srv_to_cli); //recebe nome de fifo INFO_SRV_TO_CLIXXX read_from_fifo(fd_cmd_cli_to_srv, &fifo_name_msg_srv_to_cli); //recebe nome de fifo MSG_TO_SRV_TO_CLIXXX //CIRA FIFO MSG_CLIXXX_TO_SRV char fifo_name_msg_cli_to_srv[FIFO_NAME_MAX_LEN]; strcpy(fifo_name_msg_cli_to_srv, FIFO_DIR); strcat(fifo_name_msg_cli_to_srv, "lrc_msg_cli"); strcat(fifo_name_msg_cli_to_srv, client_pid_string); strcat(fifo_name_msg_cli_to_srv, "_to_srv"); n = mkfifo(fifo_name_msg_cli_to_srv, 0660); if (n < 0) { fprintf(stderr, "error creating %s\n", fifo_name_msg_cli_to_srv); fprintf(stderr, "errno: %d\n", errno); exit(5); } //envia ao cliente a resposta ao commando /CONNECT fd_info_srv_to_cli = open(fifo_name_info_srv_to_cli, O_WRONLY); write_to_fifo(fd_info_srv_to_cli, fifo_name_msg_cli_to_srv); free(logfile); free(fifo_name_cmd_cli_to_srv); close(fd_cmd_cli_to_srv); unlink(fifo_name_cmd_cli_to_srv); unlink(fifo_name_msg_cli_to_srv); unlink(fifo_name_msg_srv_to_cli); unlink(fifo_name_info_srv_to_cli); printf("fim\n"); return 0; } client.c: #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <errno.h> #define MAX_INPUT_LENGTH 100 #define PID_BUFFER_LEN 10 #define FIFO_NAME_CMD_CLI_TO_SRV "lrc_cmd_cli_to_srv" #define FIFO_NAME_INFO_SRV_TO_CLI "lrc_info_srv_to_cli" #define FIFO_NAME_MSG_SRV_TO_CLI "lrc_msg_srv_to_cli" #define COMMAND_MAX_LEN 100 #define FIFO_DIR "/tmp/" typedef enum { false, true } bool; char* nickname; char* name; char* email; void write_to_fifo(int fd, char* data) { int n_bytes = (strlen(data)+1) * sizeof(char); write(fd, &n_bytes, sizeof(int)); //primeiro envia o numero de bytes que a proxima instrucao write ira enviar write(fd, data, n_bytes); printf("writing %d bytes '%s'\n", n_bytes, data); } void read_from_fifo(int fd, char** var) { int n_bytes; read(fd, &n_bytes, sizeof(int)); *var = (char *) malloc (n_bytes); printf("read '%s'\n", *var); read(fd, *var, n_bytes); } int main(int argc, char* argv[]) { pid_t pid = getpid(); //CRIA FIFO INFO_SRV_TO_CLIXXX char pid_string[PID_BUFFER_LEN]; sprintf(pid_string, "%d", pid); char* fifo_name_info_srv_to_cli; fifo_name_info_srv_to_cli = (char *) malloc ( (strlen(FIFO_DIR) + strlen(FIFO_NAME_INFO_SRV_TO_CLI) + strlen(pid_string) + 1 ) * sizeof(char) ); strcpy(fifo_name_info_srv_to_cli, FIFO_DIR); strcat(fifo_name_info_srv_to_cli, FIFO_NAME_INFO_SRV_TO_CLI); strcat(fifo_name_info_srv_to_cli, pid_string); int n = mkfifo(fifo_name_info_srv_to_cli, 0660); if (n < 0) { fprintf(stderr, "error creating %s\n", fifo_name_info_srv_to_cli); fprintf(stderr, "errno: %d\n", errno); exit(6); } int fd_cmd_cli_to_srv, fd_info_srv_to_cli; fd_cmd_cli_to_srv = open("/tmp/lrc_cmd_cli_to_srv", O_WRONLY); char command[COMMAND_MAX_LEN]; printf("> "); scanf("%s", command); while (strcmp(command, "/CONNECT")) { printf("O primeiro comando deverá ser \"/CONNECT\"\n"); printf("> "); scanf("%s", command); } //CRIA FIFO MSG_SRV_TO_CLIXXX char* fifo_name_msg_srv_to_cli; fifo_name_msg_srv_to_cli = (char *) malloc ( (strlen(FIFO_DIR) + strlen(FIFO_NAME_MSG_SRV_TO_CLI) + strlen(pid_string) + 1) * sizeof(char) ); strcpy(fifo_name_msg_srv_to_cli, FIFO_DIR); strcat(fifo_name_msg_srv_to_cli, FIFO_NAME_MSG_SRV_TO_CLI); strcat(fifo_name_msg_srv_to_cli, pid_string); n = mkfifo(fifo_name_msg_srv_to_cli, 0660); if (n < 0) { fprintf(stderr, "error creating %s\n", fifo_name_info_srv_to_cli); fprintf(stderr, "errno: %d\n", errno); exit(7); } // ENVIA COMANDO /CONNECT write_to_fifo(fd_cmd_cli_to_srv, pid_string); //envia pid do processo cliente write_to_fifo(fd_cmd_cli_to_srv, command); //envia commando /CONNECT write_to_fifo(fd_cmd_cli_to_srv, fifo_name_info_srv_to_cli); //envia nome de fifo INFO_SRV_TO_CLIXXX write_to_fifo(fd_cmd_cli_to_srv, fifo_name_msg_srv_to_cli); //envia nome de fifo MSG_TO_SRV_TO_CLIXXX // recebe do servidor a resposta ao comanddo /CONNECT printf("msg1\n"); printf("vamos tentar abrir %s\n", fifo_name_info_srv_to_cli); fd_info_srv_to_cli = open(fifo_name_info_srv_to_cli, O_RDONLY); printf("%s aberto", fifo_name_info_srv_to_cli); if (fd_info_srv_to_cli < 0) { fprintf(stderr, "erro ao criar %s\n", fifo_name_info_srv_to_cli); fprintf(stderr, "errno: %d\n", errno); } printf("msg2\n"); char* fifo_name_msg_cli_to_srv; printf("msg3\n"); read_from_fifo(fd_info_srv_to_cli, &fifo_name_msg_cli_to_srv); printf("msg4\n"); free(nickname); free(name); free(email); free(fifo_name_info_srv_to_cli); free(fifo_name_msg_srv_to_cli); unlink(fifo_name_msg_srv_to_cli); unlink(fifo_name_info_srv_to_cli); printf("fim\n"); return 0; } makefile: CC = gcc CFLAGS = -Wall -lpthread -fno-stack-protector all: client server client: client.c $(CC) $(CFLAGS) client.c -o client server: server.c $(CC) $(CFLAGS) server.c -o server clean: rm -f client server *~

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  • How to write a C program using the fork() system call that generates the Fibonacci sequence in the

    - by Ellen
    The problem I am having is that when say for instance the user enters 7, then the display shows: 0 11 2 3 5 8 13 21 child ends. I cannot seem to figure out how to fix the 11 and why is it displaying that many numbers in the sequence! Can anyone help? The number of the sequence will be provided in the command line. For example, if 5 is provided, the first five numbers in the Fibonacci sequence will be output by the child process. Because the parent and child processes have their own copies of the data, it will be necessary for the child to output the sequence. Have the parent invoke the wait() call to wait for the child process to complete before exiting the program. Perform necessary error checking to ensure that a non-negative number is passed on the command line. #include <stdio.h> #include <sys/types.h> #include <unistd.h> int main() { int a=0, b=1, n=a+b,i,ii; pid_t pid; printf("Enter the number of a Fibonacci Sequence:\n"); scanf("%d", &ii); if (ii < 0) printf("Please enter a non-negative integer!\n"); else { pid = fork(); if (pid == 0) { printf("Child is producing the Fibonacci Sequence...\n"); printf("%d %d",a,b); for (i=0;i<ii;i++) { n=a+b; printf("%d ", n); a=b; b=n; } printf("Child ends\n"); } else { printf("Parent is waiting for child to complete...\n"); wait(NULL); printf("Parent ends\n"); } } return 0; }

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  • Create ntp time stamp from gettimeofday

    - by krunk
    I need to calculate an ntp time stamp using gettimeofday. Below is how I've done it with comments on method. Look good to you guys? (minus error checking). Also, here's a codepad link. #include <unistd.h> #include <sys/time.h> const unsigned long EPOCH = 2208988800UL; // delta between epoch time and ntp time const double NTP_SCALE_FRAC = 4294967295.0; // maximum value of the ntp fractional part int main() { struct timeval tv; uint64_t ntp_time; uint64_t tv_ntp; double tv_usecs; gettimeofday(&tv, NULL); tv_ntp = tv.tv_sec + EPOCH; // convert tv_usec to a fraction of a second // next, we multiply this fraction times the NTP_SCALE_FRAC, which represents // the maximum value of the fraction until it rolls over to one. Thus, // .05 seconds is represented in NTP as (.05 * NTP_SCALE_FRAC) tv_usecs = (tv.tv_usec * 1e-6) * NTP_SCALE_FRAC; // next we take the tv_ntp seconds value and shift it 32 bits to the left. This puts the // seconds in the proper location for NTP time stamps. I recognize this method has an // overflow hazard if used after around the year 2106 // Next we do a bitwise AND with the tv_usecs cast as a uin32_t, dropping the fractional // part ntp_time = ((tv_ntp << 32) & (uint32_t)tv_usecs); }

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  • SUA + Visual Studio + pthreads

    - by vasek7
    Hi, I cannot compile this code under SUA: #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <pthread.h> void * thread_function(void *arg) { printf("thread_function started. Arg was %s\n", (char *)arg); // pause for 3 seconds sleep(3); // exit and return a message to another thread // that may be waiting for us to finish pthread_exit ("thread one all done"); } int main() { int res; pthread_t a_thread; void *thread_result; // create a thread that starts to run ‘thread_function’ pthread_create (&a_thread, NULL, thread_function, (void*)"thread one"); printf("Waiting for thread to finish...\n"); // now wait for new thread to finish // and get any returned message in ‘thread_result’ pthread_join(a_thread, &thread_result); printf("Thread joined, it returned %s\n", (char *)thread_result); exit(0); } I'm running on Windows 7 Ultimate x64 with Visual Studio 2008 and 2010 and I have installed: Windows Subsystem for UNIX Utilities and SDK for Subsystem for UNIX-based Applications in Microsoft Windows 7 and Windows Server 2008 R2 Include directories property of Visual Studio project is set to "C:\Windows\SUA\usr\include" What I have to configure in order to compile and run (and possibly debug) pthreads programs in Visual Studio 2010 (or 2008)?

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  • Reading Serial Data From C (OSX /dev/tty)

    - by Jud Stephenson
    I am trying to read data from a bluetooth barcode scanner (KDC300) using C. Here is the code I have so far, and the program successfully establishes a bluetooth connection to the scanner, but when a barcode is scanned, no input is displayed on the screen (Eventually more will be done with the data, but we have to get it working first, right). Here is the program: #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <fcntl.h> #include <errno.h> #include <termios.h> #include <sys/ioctl.h> int main (int argc, const char * argv[]) { // define vars int STOP = 0; //char buf[255]; if(argv[1]) { int fd = open("/dev/tty.KDC1", O_RDONLY); if(fd == -1) { printf("%s", strcat("Unable to open /dev/tty.", argv[1])); } int res; while(STOP == 0) { while((res = read(fd,buf,255)) == 0); { if(res > 0) { buf[res]=0; printf("%s:%d\n", buf, res); if(buf[sizeof(buf)]=='\n') break; } } } } return 0; } If anyone has any ideas, I am at a loss on this so far. If it is any help, I can run screen /dev/tty.KDC1 and any barcodes scanned on the scanner appear in the terminal, I just can't do anything with the data. Jud

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  • C: lseek() related question.

    - by Andrei Ciobanu
    I want to write some bogus text in a file ("helloworld" text in a file called helloworld), but not starting from the beginning. I was thinking to lseek() function. If I use the following code: #include <unistd.h> #include <fcntl.h> #include <sys/stat.h> #include <sys/types.h> #include <stdlib.h> #include <stdio.h> #define fname "helloworld" #define buf_size 16 int main(){ char buffer[buf_size]; int fildes, nbytes; off_t ret; fildes = open(fname, O_CREAT | O_TRUNC | O_WRONLY, S_IRUSR | S_IWUSR); if(fildes < 0){ printf("\nCannot create file + trunc file.\n"); } //modify offset if((ret = lseek(fildes, (off_t) 10, SEEK_END)) < (off_t) 0){ fprintf(stdout, "\nCannot modify offset.\n"); } printf("ret = %d\n", (int)ret); if(write(fildes, fname, buf_size) < 0){ fprintf(stdout, "\nWrite failed.\n"); } close(fildes); return (0); } , it compiles well and it runs without any apparent errors. Still if i : cat helloworld The output is not what I expected, but: helloworld Can Where is "Can" comming from, and where are my empty spaces ? Should i expect for "zeros" instead of spaces ? If i try to open helloworld with gedit, an error occurs, complaining that the file character encoding is unknown.

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  • Pipe overwrites buffer, don't know how to overcome

    - by Kalec
    I use a simple pipe. I read with a while, 1 char at a time, I think every time I read a char I overwrite something #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <sys/wait.h> #include <string.h> int main () { int pipefd[2]; int cpid; char buf[31]; if (pipe(pipefd) == -1) { perror("pipe"); exit(EXIT_FAILURE) } cpid = fork(); if (cpid == -1) P perror("cpid"); exit(EXIT_FAILURE); } if (cpid == 0) { // child reads from pipe close (pipefd[1]); // close unused write end while (read (pipefd[0], &buf, 1)>0); printf ("Server receives: %s", buf); close (pipefd[0])l exit (EXIT_SUCCESS); } else { // parent writes to pipe close (pipefd[0]); // closing unused read end; char buf2[30]; printf("Server transmits: "); scanf ("%s", buf2); write (pipefd[1], buf2, strlen(buf2)+1); close(pipefd[1]); wait(NULL); exit(EXIT_SUCCESS); } return 0; } For example, if I input: "Flowers" it prints F and then ~6 unprintable characters

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  • Using pthread to perform matrix multiplication

    - by shadyabhi
    I have both matrices containing only ones and each array has 500 rows and columns. So, the resulting matrix should be a matrix of all elements having value 500. But, I am getting res_mat[0][0]=5000. Even other elements are also 5000. Why? #include<stdio.h> #include<pthread.h> #include<unistd.h> #include<stdlib.h> #define ROWS 500 #define COLUMNS 500 #define N_THREADS 10 int mat1[ROWS][COLUMNS],mat2[ROWS][COLUMNS],res_mat[ROWS][COLUMNS]; void *mult_thread(void *t) { /*This function calculates 50 ROWS of the matrix*/ int starting_row; starting_row = *((int *)t); starting_row = 50 * starting_row; int i,j,k; for (i = starting_row;i<starting_row+50;i++) for (j=0;j<COLUMNS;j++) for (k=0;k<ROWS;k++) res_mat[i][j] += (mat1[i][k] * mat2[k][j]); return; } void fill_matrix(int mat[ROWS][COLUMNS]) { int i,j; for(i=0;i<ROWS;i++) for(j=0;j<COLUMNS;j++) mat[i][j] = 1; } int main() { int n_threads = 10; //10 threads created bcos we have 500 rows and one thread calculates 50 rows int j=0; pthread_t p[n_threads]; fill_matrix(mat1); fill_matrix(mat2); for (j=0;j<10;j++) pthread_create(&p[j],NULL,mult_thread,&j); for (j=0;j<10;j++) pthread_join(p[j],NULL); printf("%d\n",res_mat[0][0]); return 0; }

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  • Keyboard input: how to separate keycodes received from user

    - by Iulian Serbanoiu
    Hello, I am writing an application involving user input from the keyboard. For doing it I use this way of reading the input: #include <stdio.h> #include <termios.h> #include <unistd.h> int mygetch( ) { struct termios oldt, newt; int ch; tcgetattr( STDIN_FILENO, &oldt ); newt = oldt; newt.c_lflag &= ~( ICANON | ECHO ); tcsetattr( STDIN_FILENO, TCSANOW, &newt ); ch = getchar(); tcsetattr( STDIN_FILENO, TCSANOW, &oldt ); return ch; } int main(void) { int c; do{ c = mygetch(); printf("%d\n",c); }while(c!='q'); return 0; } Everyting works fine for letters digits,tabs but when hiting DEL, LEFT, CTRL+LEFT, F8 (and others) I receive not one but 3,4,5 or even 6 characters. The question is: Is is possible to make a separation of these characters (to actually know that I only hit one key or key combination). What I would like is to have a function to return a single integer value for any type of input (letter, digit, F1-F12, DEl, PGUP, PGDOWN, CTRL+A, CTRL+ALT+A, ALT+LEFT, etc). Is this possible? I'm interested in an idea to to this, the language doesn't matter much, though I'd prefer perl or c. Thanks, Iulian

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