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• How to re-prompt after a trap return in bash?

  - by verbose

  I have a script that is supposed to trap SIGTERM and SIGTSTP. This is what I have in the main block: trap 'killHandling' TERM And in the function: killHandling () { echo received kill signal, ignoring return } ... and similar for SIGINT. The problem is one of user interface. The script prompts the user for some input, and if the SIGTERM or SIGINT occurs when the script is waiting for input, it's confusing. Here is the output in that case: Enter something: # SIGTERM received received kill signal, ignoring # shell waits at blank line for user input, user gets confused # user hits "return", which then gets read as blank input from the user # bad things happen because of the blank input I have definitely seen scripts which handle this more elegantly, like so: Enter something: # SIGTERM received received kill signal, ignoring Enter something: # re-prompts user for user input, user is not confused What is the mechanism used to accomplish the latter? Unfortunately I can't simply change my trap code to do the re-prompt as the script prompts the user for several things and what the prompt says is context-dependent. And there has to be a better way than writing context-dependent trap functions. I'd be very grateful for any pointers. Thanks!

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• pthread_join from a signal handler

  - by liv2hak

  I have a capture program which in addition do capturing data and writing it into a file also prints some statistics.The function that prints the statistics static void* report(void) { /*Print statistics*/ } is called roughly every second using an ALARM that expires every second.So The program is like void capture_program() { pthread_t report_thread while(!exit_now) { if(pthread_create(&report_thread,NULL,report,NULL)){ fprintf(stderr,"Error creating reporting thread! \n"); } /* Capturing code -------------- -------------- */ if(doreport) usleep(5); } } void *report(void *param) { while(true) { if(doreport) { doreport = 0 //access some register from hardware usleep(5) } } } The expiry of the timer sets the doreport flag.If this flag is set report() is called which clears the flag.I am using usleep to alternate between two threads in the program.This seems to work fine. I also have a signal handler to handle SIGINT (i.e CTRL+C) static void anysig(int sig) { if (sig != SIGINT) dagutil_set_signal_handler(SIG_DFL); /* Tell the main loop to exit */ exit_now = 1; return; } My question: 1) Is it safe to call pthread_join from inside the signal handler? 2) Should I use exit_now flag for the report thread as well?

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• Preventing a child process (HandbrakeCLI) from causing the parent script to exit

  - by Chris

  I have a batch conversion script to turn .mkvs of various dimensions into ipod/iphone sized .mp4s, cropping/scaling to suit. Determining the original dimensions, required crop, output file is all working fine. However, on successful completion of the first conversion, HandbrakeCLI causes the parent script to exit. Why would this be? And how can I stop it? The code, as it currently stands: #!/bin/bash find . -name "*.mkv" | while read FILE do # What would the output file be? DST=../Touch/$(dirname "$FILE") MKV=$(basename "$FILE") MP4=${MKV%%.mkv}.mp4 # If it already exists, don't overwrite it if [ -e "$DST/$MP4" ] then echo "NOT overwriting $DST/$MP4" else # Stuff to determine dimensions/cropping removed for brevity HandbrakeCLI --preset "iPhone & iPod Touch" --vb 900 --crop $crop -i "$FILE" -o "$DST/$MP4" > /dev/null 2>&1 if [ $? != 0 ] then echo "$FILE had problems" >> errors.log fi fi done I have additionally tried it with a trap, but that didn't change the behaviour (although the last trap did fire) trap "echo Handbrake SIGINT-d" SIGINT trap "echo Handbrake SIGTERM-d" SIGTERM trap "echo Handbrake EXIT-d" EXIT trap "echo Handbrake 0-d" 0

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• segfault when cd-ing into certain directories in bash

  - by user84207

  I have noticed this very strange behavior recently. After cd into certain directories, I get a segfault on the terminal. --- SIGSEGV (Segmentation fault) @ 0 (0) --- --- SIGSEGV (Segmentation fault) @ 0 (0) --- +++ killed by SIGSEGV (core dumped) +++ segmentation fault (core dumped) I proceeded to strace a bash session in which I cd into the target directory, and was able to reproduce the problem. I attached the log to this pastebin: I paste below the few lines from the read of "cd stumpwm", which is the directory in question, until the segfault. I included a few of the repetitions of calls to "rt_sigprocmask" and "brk" to give a glimpse of the pattern, which occurs for most of the strace, read(0, cd stumpwm "c", 1) = 1 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 read(0, "d", 1) = 1 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 read(0, " ", 1) = 1 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 read(0, "s", 1) = 1 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 read(0, "t", 1) = 1 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 read(0, "u", 1) = 1 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 read(0, "m", 1) = 1 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 read(0, "p", 1) = 1 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 read(0, "w", 1) = 1 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 read(0, "m", 1) = 1 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 read(0, "\n", 1) = 1 rt_sigprocmask(SIG_BLOCK, [INT], [], 8) = 0 ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig -icanon -echo ...}) = 0 ioctl(0, SNDCTL_TMR_STOP or TCSETSW, {B38400 opost isig icanon -echo ...}) = 0 ioctl(0, SNDCTL_TMR_TIMEBASE or TCGETS, {B38400 opost isig icanon -echo ...}) = 0 rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 rt_sigaction(SIGINT, {0x457d50, [], SA_RESTORER, 0x7ffff76254a0}, {0x49edc0, [], SA_RESTORER, 0x7ffff76254a0}, 8) = 0 rt_sigaction(SIGTERM, {SIG_IGN, [], SA_RESTORER, 0x7ffff76254a0}, {SIG_IGN, [], SA_RESTORER, 0x7ffff76254a0}, 8) = 0 rt_sigaction(SIGQUIT, {SIG_IGN, [], SA_RESTORER, 0x7ffff76254a0}, {SIG_IGN, [], SA_RESTORER, 0x7ffff76254a0}, 8) = 0 rt_sigaction(SIGALRM, {0x457f50, [HUP INT ILL TRAP ABRT BUS FPE USR1 SEGV USR2 PIPE ALRM TERM XCPU XFSZ VTALRM SYS], SA_RESTORER, 0x7ffff76254a0}, {0x49edc0, [], SA_RESTORER, 0x7ffff76254a0}, 8) = 0 rt_sigaction(SIGTSTP, {SIG_IGN, [], SA_RESTORER, 0x7ffff76254a0}, {SIG_IGN, [], SA_RESTORER, 0x7ffff76254a0}, 8) = 0 rt_sigaction(SIGTTOU, {SIG_IGN, [], SA_RESTORER, 0x7ffff76254a0}, {SIG_IGN, [], SA_RESTORER, 0x7ffff76254a0}, 8) = 0 rt_sigaction(SIGTTIN, {SIG_IGN, [], SA_RESTORER, 0x7ffff76254a0}, {SIG_IGN, [], SA_RESTORER, 0x7ffff76254a0}, 8) = 0 rt_sigaction(SIGWINCH, {0x457920, [], SA_RESTORER, 0x7ffff76254a0}, {0x49e6e0, [], SA_RESTORER|SA_RESTART, 0x7ffff76254a0}, 8) = 0 rt_sigaction(SIGINT, {0x457d50, [], SA_RESTORER, 0x7ffff76254a0}, {0x457d50, [], SA_RESTORER, 0x7ffff76254a0}, 8) = 0 brk(0xa9a000) = 0xa9a000 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 brk(0xa9b000) = 0xa9b000 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 brk(0xa9c000) = 0xa9c000 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 brk(0xa9d000) = 0xa9d000 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 brk(0xa9e000) = 0xa9e000 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 brk(0xa9f000) = 0xa9f000 brk(0xaa0000) = 0xaa0000 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 brk(0xaa1000) = 0xaa1000 brk(0xaa2000) = 0xaa2000 (pattern of rt_sigprocmask, brk continues ...) rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 brk(0x1d5b000) = 0x1d5b000 brk(0x1d5c000) = 0x1d5c000 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 brk(0x1d5d000) = 0x1d5d000 brk(0x1d5e000) = 0x1d5e000 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 rt_sigprocmask(SIG_BLOCK, NULL, [], 8) = 0 --- SIGSEGV (Segmentation fault) @ 0 (0) --- --- SIGSEGV (Segmentation fault) @ 0 (0) --- +++ killed by SIGSEGV (core dumped) +++ segmentation fault (core dumped) How can I debug this? Is this likely to be a bash problem? The error does not occur with another shell, such as eshell. I have also run an fschk, although I haven't been able to see the output because of this bug.

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• Socat and rich terminals (with Ctrl+C/Ctrl+Z/Ctrl+D propagation)

  - by Vi

  socat - exec:'bash -li',pty,stderr,ctty - bash: no job control in this shell What options should I use to get fully fledged shell as I get with ssh/sshd? I want to be able to connect the shell to everything socat can handle (SOCKS 5, UDP, OpenSSL), but also to have a nice shell which correctly interprets all keys, various Ctrl+C/Ctrl+Z, tab completion, up/down keys (with remote history). Update: Found "setsid" socat option. It fixes "no job control". Now trying to fix Ctrl+D. Update 2: socat file:`tty`,raw,echo=0 exec:'bash -li',pty,stderr,setsid,sigint,sane. Not it handles Ctrl+D/Ctrl+Z/Ctrl+C well, I can start Vim inside it, remote history is OK.

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• Running command transparently over ssh

  - by jnsg

  By transparently I mean forwarding of: stdin, stdout and stderr standard signals (SIGHUP or SIGINT would be great for a start) As an example, consider these invocations of a (pointless) local and remote command: $ `cat - > /dev/null; sleep 10` < /local/file $ ssh user@host "cat - > /dev/null; sleep 10" < /local/file I can interrupt the first one with ^C just fine. But if I try this during the second one it only affects ssh, leaving the command running on the remote server if cat has already finished. I know about launching sshwith -t, but this way I can't send data via stdin. Is this possible with ssh alone at all?

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• Ways to remotely reboot a Linux system

  - by dualed

  I had a remote server running Debian Sarge that experienced some HDD failure and I meant to reboot it hoping that fsck could repair the errors automatically. I eventually drove out there and replaced the faulty disks... But I was wondering: What other ways are there to force a Linux system to reboot that do not require hard drive access? What I had tried: shutdown -r now Did not work, as shutdown is a program that would have to be loaded from disk, the error shown in the terminal was bash: /sbin/shutdown: Input/output error init 6 same as above telinit q same as above kill -2 1 This did not print an error, but did not work either. (However, it is possible that the Sarge init did not implement SIGINT, the sarge manpages did not mention it. So it could work in a more recent version of Debian) This guide on PCFreak.net. However, this failed at sysctl, which was not in memory either.

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• mysql_close doesn't kill locked sql requests

  - by Nikita

  I use mysqld Ver 5.1.37-2-log for debian-linux-gnu I perform mysql calls from c++ code with functions mysql_query. The problem occurs when mysql_query execute procedure, procedure locked on locked table, so mysql_query hangs. If send kill signal to application then we can see lock until table is locked. Create the following SQL table and procedure CREATE TABLE IF NOT EXISTS `tabletolock` ( `id` INT NOT NULL AUTO_INCREMENT, PRIMARY KEY (`id`) )ENGINE = InnoDB; DELIMITER $$ DROP PROCEDURE IF EXISTS `LOCK_PROCEDURE` $$ CREATE PROCEDURE `LOCK_PROCEDURE`() BEGIN SELECT id INTO @id FROM tabletolock; END $$ DELOMITER; There are sql commands to reproduce the problem: 1. in one terminal execute lock tables tabletolock write; 2. in another terminal execute call LOCK_PROCEDURE(); 3. In first terminal exeute show processlist and see | 2492 | root | localhost | syn_db | Query | 12 | Locked | SELECT id INTO @id FROM tabletolock | Then perfrom Ctrl-C in second terminal to interrupt our procudere and see processlist again. It is not changed, we already see locked select request and can teminate it by unlock tables or kill commands. Problem described is occured with mysql command line client. Also such problem exists when we use functions mysql_query and mysql_close. Example of c code: #include <iostream> #include <mysql/mysql.h> #include <mysql/errmsg.h> #include <signal.h> // g++ -Wall -g -fPIC -lmysqlclient dbtest.cpp using namespace std; MYSQL * connection = NULL; void closeconnection() { if(connection != NULL) { cout << "close connection !\n"; mysql_close(connection); mysql_thread_end(); delete connection; mysql_library_end(); } } void sigkill(int s) { closeconnection(); signal(SIGINT, NULL); raise(s); } int main(int argc, char ** argv) { signal(SIGINT, sigkill); connection = new MYSQL; mysql_init(connection); mysql_options(connection, MYSQL_READ_DEFAULT_GROUP, "nnfc"); if (!mysql_real_connect(connection, "127.0.0.1", "user", "password", "db", 3306, NULL, CLIENT_MULTI_RESULTS)) { delete connection; cout << "cannot connect\n"; return -1; } cout << "before procedure call\n"; mysql_query(connection, "CALL LOCK_PROCEDURE();"); cout << "after procedure call\n"; closeconnection(); return 0; } Compile it, and perform the folloing actions: 1. in first terminal local tables tabletolock write; 2. run program ./a.out 3. interrupt program Ctrl-C. on the screen we see that closeconnection function is called, so connection is closed. 4. in first terminal execute show processlist and see that procedure was not intrrupted. My question is how to terminate such locked calls from c code? Thank you in advance!

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• Can't pipe echo to netcat?

  - by user1641300

  I have the following command: echo 'HTTP/1.1 200 OK\r\n' | nc -l -p 8000 -c and when I curl localhost:8000 I am not seeing HTTP/1.1 200 .. being printed. I am on mac os x with netcat 0.7.1 Any ideas? #!/bin/bash trap 'my_exit; exit' SIGINT SIGQUIT my_exit() { echo "you hit Ctrl-C/Ctrl-\, now exiting.." # cleanup commands here if any } if test $# -eq 0 ; then echo "Usage: $0 PORT" echo "" exit 1 fi while true do echo "HTTP/1.1 200 OK\r\n" | nc -l -p ${1} -c done and testing with: curl localhost:8000

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• Puppet: hanging at Schedule[weekly]

  - by Andrei Serdeliuc

  Why would puppet hang at Schedule[weekly]? I'm running puppet in a masterless setup, so to apply by manifest I'm just running puppet apply /etc/puppet/manifests/site.pp In debug mode, these are the last things it says before it just hangs debug: /Schedule[never]: Skipping device resources because running on a host debug: /Schedule[daily]: Skipping device resources because running on a host debug: /Schedule[monthly]: Skipping device resources because running on a host debug: /Schedule[puppet]: Skipping device resources because running on a host debug: /Schedule[hourly]: Skipping device resources because running on a host debug: /Schedule[weekly]: Skipping device resources because running on a host If I send a SIGINT, it says Exiting debug: Storing state debug: Stored state in 0.03 seconds debug: Finishing transaction 69992657242500 Thanks

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• Problems debugging using Cygwin gdb in Eclipse CDT(Helios)

  - by Rohan

  I am trying to debug an application using Eclipse CDT and cygwin gdb and I am facing a problem if my code calls Sleep(), it looks like whenever a sleep is encountered in the code the debugger seems to go in an infinite loop(I meant it never terminates or hit a breakpoint after sleep). On pressing pause the code is stuck on one of the thread on sigint::interrupt. Even my debugger console windows throw these error in the console output: [New thread 5968.0x1f98] Error: dll starting at 0x774a0000 not found. Error: dll starting at 0x775c0000 not found. [New thread 5968.0x19e8] Any idea what are these errors about? It would be helpful if someone can help me out here as I am new to eclipse and I am used to using VS so it has made be lazy to be honest and expect things to work out of box. Here are more details if required Windows 7 x64 bit. Eclipse 3.6 Helios with CDT plug-in compiled from the CVS head. Cygwin latest from website, I think it is 1.71

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• MPI signal handling

  - by Seth Johnson

  When using mpirun, is it possible to catch signals (for example, the SIGINT generated by ^C) in the code being run? For example, I'm running a parallelized python code. I can except KeyboardInterrupt to catch those errors when running python blah.py by itself, but I can't when doing mpirun -np 1 python blah.py. Does anyone have a suggestion? Even finding how to catch signals in a C or C++ compiled program would be a helpful start. If I send a signal to the spawned Python processes, they can handle the signals properly; however, signals sent to the parent orterun process (i.e. from exceeding wall time on a cluster, or pressing control-C in a terminal) will kill everything immediately.

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• Permission Problem While Installing Module With CPAN

  - by neversaint

  I tried to following module using CPAN, but the message I get is the "I have neither the -x permission ..." . How can I resolve that? cpan[3]> install List::MoreUtils is it OK to try to connect to the Internet? [yes] Fetching with LWP: http://www.perl.org/CPAN/authors/id/V/VP/VPARSEVAL/List-MoreUtils-0.22.tar.gz CPAN: Digest::SHA loaded ok (v5.48) Fetching with LWP: http://www.perl.org/CPAN/authors/id/V/VP/VPARSEVAL/CHECKSUMS Checksum for /home/ewijaya/.cpan/sources/authors/id/V/VP/VPARSEVAL/List-MoreUtils-0.22.tar.gz ok Scanning cache /home/neversaint/.cpan/build for sizes .....I have neither the -x permission nor the permission to change the permission; cannot estimate disk usage of '/home/neversaint/.cpan/build/Module-Build-0.3607-Kvb1Vq' .I have neither the -x permission nor the permission to change the permission; cannot estimate disk usage of '/home/neversaint/.cpan/build/ExtUtils-ParseXS-2.2205-zuX4x2' ^CCaught SIGINT, trying to continue

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• Problems debugging using Cygwin gdb in Eclipse CDT(Helios)

  - by Rohan

  I am trying to debug an application using Eclipse CDT and cygwin gdb and I am facing a problem if my code calls Sleep(), it looks like whenever a sleep is encountered in the code the debugger seems to go in an infinite loop(I meant it never terminates or hit a breakpoint after sleep). On pressing pause the code is stuck on one of the thread on sigint::interrupt. Even my debugger console windows throw these error in the console output: [New thread 5968.0x1f98] Error: dll starting at 0x774a0000 not found. Error: dll starting at 0x775c0000 not found. [New thread 5968.0x19e8] Any idea what are these errors about? It would be helpful if someone can help me out here as I am new to eclipse and I am used to using VS so it has made be lazy to be honest and expect things to work out of box. Here are more details if required Windows 7 x64 bit. Eclipse 3.6 Helios with CDT plug-in compiled from the CVS head. Cygwin latest from website, I think it is 1.71

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• cpan won't configure correctly on centos6, can't connect to internet

  - by dan

  I have Centos 6 setup and have installed perl-CPAN. When I run cpan it takes me through the setup and ends by telling me it can't connect to the internet and to enter a mirror. I enter a mirror, but it still can't install the package. What am I doing wrong? If you're accessing the net via proxies, you can specify them in the CPAN configuration or via environment variables. The variable in the $CPAN::Config takes precedence. <ftp_proxy> Your ftp_proxy? [] <http_proxy> Your http_proxy? [] <no_proxy> Your no_proxy? [] CPAN needs access to at least one CPAN mirror. As you did not allow me to connect to the internet you need to supply a valid CPAN URL now. Please enter the URL of your CPAN mirror CPAN needs access to at least one CPAN mirror. As you did not allow me to connect to the internet you need to supply a valid CPAN URL now. Please enter the URL of your CPAN mirror mirror.cc.columbia.edu::cpan Configuration does not allow connecting to the internet. Current set of CPAN URLs: mirror.cc.columbia.edu::cpan Enter another URL or RETURN to quit: [] New urllist mirror.cc.columbia.edu::cpan Please remember to call 'o conf commit' to make the config permanent! cpan shell -- CPAN exploration and modules installation (v1.9402) Enter 'h' for help. cpan[1]> install File::Stat CPAN: Storable loaded ok (v2.20) LWP not available Warning: no success downloading '/root/.cpan/sources/authors/01mailrc.txt.gz.tmp918'. Giving up on it. at /usr/share/perl5/CPAN/Index.pm line 225 ^CCaught SIGINT, trying to continue Warning: Cannot install File::Stat, don't know what it is. Try the command i /File::Stat/ to find objects with matching identifiers. cpan[2]>

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• Detect user logout / shutdown in Python / GTK under Linux

  - by Ivo Wetzel

  OK this is presumably a hard one, I've got an pyGTK application that has random crashes due to X Window errors that I can't catch/control. So I created a wrapper that restarts the app as soon as it detects a crash, now comes the problem, when the user logs out or shuts down the system, the app exits with status 1. But on some X errors it does so too. So I tried literally anything to catch the shutdown/logout, with no success, here's what I've tried: import pygtk import gtk import sys class Test(gtk.Window): def delete_event(self, widget, event, data=None): open("delete_event", "wb") def destroy_event(self, widget, data=None): open("destroy_event", "wb") def destroy_event2(self, widget, event, data=None): open("destroy_event2", "wb") def __init__(self): gtk.Window.__init__(self, gtk.WINDOW_TOPLEVEL) self.show() self.connect("delete_event", self.delete_event) self.connect("destroy", self.destroy_event) self.connect("destroy-event", self.destroy_event2) def foo(): open("add_event", "wb") def ex(): open("sys_event", "wb") from signal import * def clean(sig): f = open("sig_event", "wb") f.write(str(sig)) f.close() exit(0) for sig in (SIGABRT, SIGILL, SIGINT, SIGSEGV, SIGTERM): signal(sig, lambda *args: clean(sig)) def at(): open("at_event", "wb") import atexit atexit.register(at) f = Test() sys.exitfunc = ex gtk.quit_add(gtk.main_level(), foo) gtk.main() open("exit_event", "wb") Not one of these succeeds, is there any low level way to detect the system shutdown? Google didn't find anything related to that. I guess there must be a way, am I right? :/

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• ImportError: No module named QtWebKit

  - by Hallik

  I am on centos5. I installed python26 source with a make altinstall. Then I did a: yum install qt4 yum install qt4-devel yum install qt4-doc From riverbankcomputing.co.uk I downloaded the source for sip 4.10.2, compiled and installed fine. Then from the same site I downloaded and compiled from source PyQt-x11-4.7.3 Both installs were using the python26 version (/usr/local/bin/python2.6). So configure.py, make, and make install worked with no errors. Finally, I tried to run this script, but got the error in the subject of this post: import sys import signal from PyQt4.QtCore import * from PyQt4.QtGui import * from PyQt4.QtWebKit import QWebPage def onLoadFinished(result): if not result: print "Request failed" sys.exit(1) #screen = QtGui.QDesktopWidget().screenGeometry() size = webpage.mainFrame().contentsSize() # Set the size of the (virtual) browser window webpage.setViewportSize(webpage.mainFrame().contentsSize()) # Paint this frame into an image image = QImage(webpage.viewportSize(), QImage.Format_ARGB32) painter = QPainter(image) webpage.mainFrame().render(painter) painter.end() image.save("output2.png") sys.exit(0) app = QApplication(sys.argv) signal.signal(signal.SIGINT, signal.SIG_DFL) webpage = QWebPage() webpage.connect(webpage, SIGNAL("loadFinished(bool)"), onLoadFinished) webpage.mainFrame().load(QUrl("http://www.google.com")) sys.exit(app.exec_()) Even in the beginning of the configure for pyqt4, I saw it say QtWebKit should be installed, but apparently it's not? What's going on? I just did a find, and it looks like it wasn't installed. What are my options? [root@localhost ~]# find / -name '*QtWebKit*' /root/PyQt-x11-gpl-4.7.3/sip/QtWebKit /root/PyQt-x11-gpl-4.7.3/sip/QtWebKit/QtWebKitmod.sip /root/PyQt-x11-gpl-4.7.3/cfgtest_QtWebKit.cpp

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• How to properly handle signals when using the worker thread pattern?

  - by ipartola

  I have a simple server that looks something like this: void *run_thread(void *arg) { // Communicate via a blocking socket } int main() { // Initialization happens here... // Main event loop while (1) { new_client = accept(socket, ...); pthread_create(&thread, NULL, &run_thread, *thread_data*); pthread_detach(thread); } // Do cleanup stuff: close(socket); // Wait for existing threads to finish exit(0); ) Thus when a SIGINT or SIGTERM is received I need to break out of the main event loop to get to the clean up code. Moreover most likely the master thread is waiting on the accept() call so it's not able to check some other variable to see if it should break;. Most of the advice I found was along the lines of this: http://devcry.blogspot.com/2009/05/pthreads-and-unix-signals.html (creating a special signal handling thread to catch all the signals and do processing on those). However, it's the processing portion that I can't really wrap my head around: how can I possibly tell the main thread to return from the accept() call and check on an external variable to see if it should break;?

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• Pthread - setting scheduler parameters

  - by Andna

  I wanted to use read-writer locks from pthread library in a way, that writers have priority over readers. I read in my man pages that If the Thread Execution Scheduling option is supported, and the threads involved in the lock are executing with the scheduling policies SCHED_FIFO or SCHED_RR, the calling thread shall not acquire the lock if a writer holds the lock or if writers of higher or equal priority are blocked on the lock; otherwise, the calling thread shall acquire the lock. so I wrote small function that sets up thread scheduling options. void thread_set_up(int _thread) { struct sched_param *_param=malloc(sizeof (struct sched_param)); int *c=malloc(sizeof(int)); *c=sched_get_priority_min(SCHED_FIFO)+1; _param->__sched_priority=*c; long *a=malloc(sizeof(long)); *a=syscall(SYS_gettid); int *b=malloc(sizeof(int)); *b=SCHED_FIFO; if (pthread_setschedparam(*a,*b,_param) == -1) { //depending on which thread calls this functions, few thing can happen if (_thread == MAIN_THREAD) client_cleanup(); else if (_thread==ACCEPT_THREAD) { pthread_kill(params.main_thread_id,SIGINT); pthread_exit(NULL); } } } sorry for those a,b,c but I tried to malloc everything, still I get SIGSEGV on the call to pthread_setschedparam, I am wondering why?

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• Detect user logout / shutdown in Python / GTK under Linux - SIGTERM/HUP not received

  - by Ivo Wetzel

  OK this is presumably a hard one, I've got an pyGTK application that has random crashes due to X Window errors that I can't catch/control. So I created a wrapper that restarts the app as soon as it detects a crash, now comes the problem, when the user logs out or shuts down the system, the app exits with status 1. But on some X errors it does so too. So I tried literally anything to catch the shutdown/logout, with no success, here's what I've tried: import pygtk import gtk import sys class Test(gtk.Window): def delete_event(self, widget, event, data=None): open("delete_event", "wb") def destroy_event(self, widget, data=None): open("destroy_event", "wb") def destroy_event2(self, widget, event, data=None): open("destroy_event2", "wb") def __init__(self): gtk.Window.__init__(self, gtk.WINDOW_TOPLEVEL) self.show() self.connect("delete_event", self.delete_event) self.connect("destroy", self.destroy_event) self.connect("destroy-event", self.destroy_event2) def foo(): open("add_event", "wb") def ex(): open("sys_event", "wb") from signal import * def clean(sig): f = open("sig_event", "wb") f.write(str(sig)) f.close() exit(0) for sig in (SIGABRT, SIGILL, SIGINT, SIGSEGV, SIGTERM): signal(sig, lambda *args: clean(sig)) def at(): open("at_event", "wb") import atexit atexit.register(at) f = Test() sys.exitfunc = ex gtk.quit_add(gtk.main_level(), foo) gtk.main() open("exit_event", "wb") Not one of these succeeds, is there any low level way to detect the system shutdown? Google didn't find anything related to that. I guess there must be a way, am I right? :/ EDIT: OK, more stuff. I've created this shell script: #!/bin/bash trap test_term TERM trap test_hup HUP test_term(){ echo "teeeeeeeeeerm" >~/Desktop/term.info exit 0 } test_hup(){ echo "huuuuuuuuuuup" >~/Desktop/hup.info exit 1 } while [ true ] do echo "idle..." sleep 2 done And also created a .desktop file to run it: [Desktop Entry] Name=Kittens GenericName=Kittens Comment=Kitten Script Exec=kittens StartupNotify=true Terminal=false Encoding=UTF-8 Type=Application Categories=Network;GTK; Name[de_DE]=Kittens Normally this should create the term file on logout and the hup file when it has been started with &. But not on my System. GDM doesn't care about the script at all, when I relog, it's still running. I've also tried using shopt -s huponexit, with no success. EDIT2: Also here's some more information aboute the real code, the whole thing looks like this: Wrapper Script, that catches errors and restarts the programm -> Main Programm with GTK Mainloop -> Background Updater Thread The flow is like this: Start Wrapper -> enter restart loop while restarts < max: -> start program -> check return code -> write error to file or exit the wrapper on 0 Now on shutdown, start program return 1. That means either it did hanup or the parent process terminated, the main problem is to figure out which of these two did just happen. X Errors result in a 1 too. Trapping in the shellscript doesn't work. If you want to take a look at the actual code check it out over at GitHub: http://github.com/BonsaiDen/Atarashii

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• Wake up thread blocked on accept() call

  - by selbie

  Sockets on Linux question I have a worker thread that is blocked on an accept() call. It simply waits for an incoming network connection, handles it, and then returns to listening for the next connection. When it is time for the program to exit, how do I signal this network worker thread (from the main thread) to return from the accept() call while still being able to gracefully exit its loop and handle it's cleanup code. Some things I tried: 1. pthread_kill to send a signal. Feels kludgy to do this, plus it doesn't reliably allow the thread to do it's shutdown logic. Also makes the program terminate as well. I'd like to avoid signals if at all possible. pthread_cancel. Same as above. It's a harsh kill on the thread. That, and the thread may be doing something else. Closing the listen socket from the main thread in order to make accept() abort. This doesn't reliably work. Some constraints: If the solution involves making the listen socket non-blocking, that is fine. But I don't want to accept a solution that involves the thread waking up via a select call every few seconds to check the exit condition. The thread condition to exit may not be tied to the process exiting. Essentially, the logic I am going for looks like this. void* WorkerThread(void* args) { DoSomeImportantInitialization(); // initialize listen socket and some thread specific stuff while (HasExitConditionBeenSet()==false) { listensize = sizeof(listenaddr); int sock = accept(listensocket, &listenaddr, &listensize); // check if exit condition has been set using thread safe semantics if (HasExitConditionBeenSet()) { break; } if (sock < 0) { printf("accept returned %d (errno==%d)\n", sock, errno); } else { HandleNewNetworkCondition(sock, &listenaddr); } } DoSomeImportantCleanup(); // close listen socket, close connections, cleanup etc.. return NULL; } void SignalHandler(int sig) { printf("Caught CTRL-C\n"); } void NotifyWorkerThreadToExit(pthread_t thread_handle) { // signal thread to exit } int main() { void* ptr_ret= NULL; pthread_t workerthread_handle = 0; pthread_create(&workerthread, NULL, WorkerThread, NULL); signal(SIGINT, SignalHandler); sleep((unsigned int)-1); // sleep until the user hits ctrl-c printf("Returned from sleep call...\n"); SetThreadExitCondition(); // sets global variable with barrier that worker thread checks on // this is the function I'm stalled on writing NotifyWorkerThreadToExit(workerthread_handle); // wait for thread to exit cleanly pthread_join(workerthread_handle, &ptr_ret); DoProcessCleanupStuff(); }

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• Can't import my module when start my twisted application under root

  - by kepkin

  Here is absolutely minimal application so you could try to reproduce it on your machine. Having two files for example in /home/aln/tmp/tw_test: server.tac MyLib.py MyLib.py class Solver(object): def solve(self): """ do extremely complex stuff here """ print "Hello from solve" server.tac #!/usr/bin/python import MyLib from twisted.application import internet, service from twisted.internet import protocol, reactor, defer, utils, threads from twisted.protocols import basic class MyProtocol(basic.LineReceiver): def lineReceived(self, line): if line=="new job": self.transport.write("started a job" + '\r\n') self.factory.run_defered() class MyFactory(protocol.ServerFactory, MyLib.Solver): protocol = MyProtocol def run_defered_helper(self): self.solve() def run_defered(self): d = threads.deferToThread(self.run_defered_helper) application = service.Application('MyApplication') factory = MyFactory() internet.TCPServer(1079, factory).setServiceParent(service.IServiceCollection(application)) Everything works fine when I start it under non-root user. aln@aln-laptop:tw_test$ twistd -ny server.tac 2010-03-03 22:42:55+0300 [-] Log opened. 2010-03-03 22:42:55+0300 [-] twistd 8.2.0 (/usr/bin/python 2.6.4) starting up. 2010-03-03 22:42:55+0300 [-] reactor class: twisted.internet.selectreactor.SelectReactor. 2010-03-03 22:42:55+0300 [-] <class 'MyFactory'> starting on 1079 2010-03-03 22:42:55+0300 [-] Starting factory <MyFactory object at 0x2d5ea50> 2010-03-03 22:42:59+0300 [MyProtocol,0,127.0.0.1] Hello from solve ^C2010-03-03 22:43:01+0300 [-] Received SIGINT, shutting down. 2010-03-03 22:43:01+0300 [-] (Port 1079 Closed) 2010-03-03 22:43:01+0300 [-] Stopping factory <MyFactory object at 0x2d5ea50> 2010-03-03 22:43:01+0300 [-] Main loop terminated. 2010-03-03 22:43:02+0300 [-] Server Shut Down. But if try to start it under root (which is going to happen in my real application) I receive the following exception: aln@aln-laptop:tw_test$ sudo twistd -ny server.tac [sudo] password for aln: Traceback (most recent call last): File "/usr/lib/python2.6/dist-packages/twisted/application/app.py", line 694, in run runApp(config) File "/usr/lib/python2.6/dist-packages/twisted/scripts/twistd.py", line 23, in runApp _SomeApplicationRunner(config).run() File "/usr/lib/python2.6/dist-packages/twisted/application/app.py", line 411, in run self.application = self.createOrGetApplication() File "/usr/lib/python2.6/dist-packages/twisted/application/app.py", line 494, in createOrGetApplication application = getApplication(self.config, passphrase) --- <exception caught here> --- File "/usr/lib/python2.6/dist-packages/twisted/application/app.py", line 505, in getApplication application = service.loadApplication(filename, style, passphrase) File "/usr/lib/python2.6/dist-packages/twisted/application/service.py", line 390, in loadApplication application = sob.loadValueFromFile(filename, 'application', passphrase) File "/usr/lib/python2.6/dist-packages/twisted/persisted/sob.py", line 215, in loadValueFromFile exec fileObj in d, d File "server.tac", line 2, in <module> import MyLib exceptions.ImportError: No module named MyLib Failed to load application: No module named MyLib If I try to load MyLib module in the python intepreter under root, it works fine: aln@aln-laptop:tw_test$ sudo python Python 2.6.4 (r264:75706, Dec 7 2009, 18:43:55) [GCC 4.4.1] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import MyLib >>> import sys >>> print(sys.path) ['', '/usr/lib/python2.6', '/usr/lib/python2.6/plat-linux2', '/usr/lib/python2.6/lib-tk', '/usr/lib/python2.6/lib-old', '/usr/lib/python2.6/lib-dynload', '/usr/lib/python2.6/dist-packages', '/usr/lib/python2.6/dist-packages/PIL', '/usr/lib/python2.6/dist-packages/gst-0.10', '/usr/lib/pymodules/python2.6', '/usr/lib/python2.6/dist-packages/gtk-2.0', '/usr/lib/pymodules/python2.6/gtk-2.0', '/usr/local/lib/python2.6/dist-packages'] >>> sys.path is absolutely the same for aln user. I tried sudo -E too. Any suggestions?

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• Confusion related to sigwait in multiprocess system

  - by user34790

  I am having difficulty in understanding IPC in multiprocess system. I have this system where there are three child processes that send two types of signals to their process group. There are four types of signal handling processes responsible for a particular type of signal. There is this monitoring process which waits for both the signals and then processes accordingly. When I run this program for a while, the monitoring process doesn't seem to pick up the signal as well as the signal handling process. I could see in the log that the signal is only being generated but not handled at all. My code is given below #include <cstdlib> #include <iostream> #include <iomanip> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> #include <sys/time.h> #include <signal.h> #include <unistd.h> #include <fcntl.h> #include <cstdio> #include <stdlib.h> #include <stdio.h> #include <pthread.h> using namespace std; double timestamp() { struct timeval tp; gettimeofday(&tp, NULL); return (double)tp.tv_sec + tp.tv_usec / 1000000.; } double getinterval() { srand(time(NULL)); int r = rand()%10 + 1; double s = (double)r/100; } int count; int count_1; int count_2; double time_1[10]; double time_2[10]; pid_t senders[1]; pid_t handlers[4]; pid_t reporter; void catcher(int sig) { printf("Signal catcher called for %d",sig); } int main(int argc, char *argv[]) { void signal_catcher_int(int); pid_t pid,w; int status; if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("1"); return 1; } if(signal(SIGUSR2 ,SIG_IGN) == SIG_ERR) { perror("2"); return 2; } if(signal(SIGINT,signal_catcher_int) == SIG_ERR) { perror("3"); return 2; } //Registering the signal handler for(int i=0; i<4; i++) { if((pid = fork()) == 0) { cout << i << endl; //struct sigaction sigact; sigset_t sigset; int sig; int result = 0; sigemptyset(&sigset); if(i%2 == 0) { if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); return 2; } sigaddset(&sigset, SIGUSR1); sigprocmask(SIG_BLOCK, &sigset, NULL); } else { if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("2"); return 2; } sigaddset(&sigset, SIGUSR2); sigprocmask(SIG_BLOCK, &sigset, NULL); } while(true) { int result = sigwait(&sigset, &sig); if(result == 0) { cout << "The caught signal is " << sig << endl; } } exit(0); } else { cout << "Registerd the handler " << pid << endl; handlers[i] = pid; } } //Registering the monitoring process if((pid = fork()) == 0) { sigset_t sigset; int sig; int result = 0; sigemptyset(&sigset); sigaddset(&sigset, SIGUSR1); sigaddset(&sigset, SIGUSR2); sigprocmask(SIG_BLOCK, &sigset, NULL); while(true) { int result = sigwait(&sigset, &sig); if(result == 0) { cout << "The monitored signal is " << sig << endl; } else { cout << "error" << endl; } } } else { reporter = pid; } sleep(3); //Registering the signal generator for(int i=0; i<1; i++) { if((pid = fork()) == 0) { if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("1"); return 1; } if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); return 2; } srand(time(0)); while(true) { volatile int signal_id = rand()%2 + 1; cout << "Generating the signal " << signal_id << endl; if(signal_id == 1) { killpg(getpgid(getpid()), SIGUSR1); } else { killpg(getpgid(getpid()), SIGUSR2); } int r = rand()%10 + 1; double s = (double)r/100; sleep(s); } exit(0); } else { cout << "Registered the sender " << pid << endl; senders[i] = pid; } } while(w = wait(&status)) { cout << "Wait on PID " << w << endl; } } void signal_catcher_int(int the_sig) { //cout << "Handling the Ctrl C signal " << endl; for(int i=0; i<1; i++) { kill(senders[i],SIGKILL); } for(int i=0; i<4; i++) { kill(handlers[i],SIGKILL); } kill(reporter,SIGKILL); exit(3); } Any suggestions? Here is a sample of the output as well In the beginning Registerd the handler 9544 Registerd the handler 9545 1 Registerd the handler 9546 Registerd the handler 9547 2 3 0 Registered the sender 9550 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 2 The caught signal is 12 The caught signal is 12 The monitored signal is 12 Generating the signal 2 Generating the signal 2 The caught signal is 12 The caught signal is 12 Generating the signal 1 The caught signal is 12 The monitored signal is 10 The monitored signal is 12 Generating the signal 1 Generating the signal 2 The caught signal is 12 Generating the signal 1 Generating the signal 2 10 The monitored signal is 10 The caught signal is 12 Generating the signal 1 The caught signal is 12 The monitored signal is GenThe caught signal is TheThe caught signal is 10 Generating the signal 2 Later on The monitored signal is GenThe monitored signal is 10 Generating the signal 1 Generating the signal 2 The caught signal is 10 The caught signal is 10 The caught signal is 10 The caught signal is 12 Generating the signal 1 Generating the signal 2 Generating the signal 1 Generating the signal 1 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 1 The caught signal is 12 The caught signal is 10 The caught signal is 10 Generating the signal 2 Generating the signal 1 Generating the signal 1 Generating the signal 2 Generating the signal 1 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 1 Generating the signal 2 Generating the signal 1 Generating the signal 2 Generating the signal 2 The caught signal is 10 Generating the signal 2 Generating the signal 1 Generating the signal 1 As you can see initially, the signal was generated and handled both by my signal handlers and monitoring processes. But later on the signal was generated a lot, but it was not quite processes in the same magnitude as before. Further I could see very less signal processing by the monitoring process Can anyone please provide some insights. What's going on?

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• Why should main() be short?

  - by Stargazer712

  I've been programming for over 9 years, and according to the advice of my first programming teacher, I always keep my main() function extremely short. At first I had no idea why. I just obeyed without understanding, much to the delight of my professors. After gaining experience, I realized that if I designed my code correctly, having a short main() function just sortof happened. Writing modularized code and following the single responsibility principle allowed my code to be designed in "bunches", and main() served as nothing more than a catalyst to get the program running. Fast forward to a few weeks ago, I was looking at Python's souce code, and I found the main() function: /* Minimal main program -- everything is loaded from the library */ ... int main(int argc, char **argv) { ... return Py_Main(argc, argv); } Yay Python. Short main() function == Good code. Programming teachers were right. Wanting to look deeper, I took a look at Py_Main. In its entirety, it is defined as follows: /* Main program */ int Py_Main(int argc, char **argv) { int c; int sts; char *command = NULL; char *filename = NULL; char *module = NULL; FILE *fp = stdin; char *p; int unbuffered = 0; int skipfirstline = 0; int stdin_is_interactive = 0; int help = 0; int version = 0; int saw_unbuffered_flag = 0; PyCompilerFlags cf; cf.cf_flags = 0; orig_argc = argc; /* For Py_GetArgcArgv() */ orig_argv = argv; #ifdef RISCOS Py_RISCOSWimpFlag = 0; #endif PySys_ResetWarnOptions(); while ((c = _PyOS_GetOpt(argc, argv, PROGRAM_OPTS)) != EOF) { if (c == 'c') { /* -c is the last option; following arguments that look like options are left for the command to interpret. */ command = (char *)malloc(strlen(_PyOS_optarg) + 2); if (command == NULL) Py_FatalError( "not enough memory to copy -c argument"); strcpy(command, _PyOS_optarg); strcat(command, "\n"); break; } if (c == 'm') { /* -m is the last option; following arguments that look like options are left for the module to interpret. */ module = (char *)malloc(strlen(_PyOS_optarg) + 2); if (module == NULL) Py_FatalError( "not enough memory to copy -m argument"); strcpy(module, _PyOS_optarg); break; } switch (c) { case 'b': Py_BytesWarningFlag++; break; case 'd': Py_DebugFlag++; break; case '3': Py_Py3kWarningFlag++; if (!Py_DivisionWarningFlag) Py_DivisionWarningFlag = 1; break; case 'Q': if (strcmp(_PyOS_optarg, "old") == 0) { Py_DivisionWarningFlag = 0; break; } if (strcmp(_PyOS_optarg, "warn") == 0) { Py_DivisionWarningFlag = 1; break; } if (strcmp(_PyOS_optarg, "warnall") == 0) { Py_DivisionWarningFlag = 2; break; } if (strcmp(_PyOS_optarg, "new") == 0) { /* This only affects __main__ */ cf.cf_flags |= CO_FUTURE_DIVISION; /* And this tells the eval loop to treat BINARY_DIVIDE as BINARY_TRUE_DIVIDE */ _Py_QnewFlag = 1; break; } fprintf(stderr, "-Q option should be `-Qold', " "`-Qwarn', `-Qwarnall', or `-Qnew' only\n"); return usage(2, argv[0]); /* NOTREACHED */ case 'i': Py_InspectFlag++; Py_InteractiveFlag++; break; /* case 'J': reserved for Jython */ case 'O': Py_OptimizeFlag++; break; case 'B': Py_DontWriteBytecodeFlag++; break; case 's': Py_NoUserSiteDirectory++; break; case 'S': Py_NoSiteFlag++; break; case 'E': Py_IgnoreEnvironmentFlag++; break; case 't': Py_TabcheckFlag++; break; case 'u': unbuffered++; saw_unbuffered_flag = 1; break; case 'v': Py_VerboseFlag++; break; #ifdef RISCOS case 'w': Py_RISCOSWimpFlag = 1; break; #endif case 'x': skipfirstline = 1; break; /* case 'X': reserved for implementation-specific arguments */ case 'U': Py_UnicodeFlag++; break; case 'h': case '?': help++; break; case 'V': version++; break; case 'W': PySys_AddWarnOption(_PyOS_optarg); break; /* This space reserved for other options */ default: return usage(2, argv[0]); /*NOTREACHED*/ } } if (help) return usage(0, argv[0]); if (version) { fprintf(stderr, "Python %s\n", PY_VERSION); return 0; } if (Py_Py3kWarningFlag && !Py_TabcheckFlag) /* -3 implies -t (but not -tt) */ Py_TabcheckFlag = 1; if (!Py_InspectFlag && (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') Py_InspectFlag = 1; if (!saw_unbuffered_flag && (p = Py_GETENV("PYTHONUNBUFFERED")) && *p != '\0') unbuffered = 1; if (!Py_NoUserSiteDirectory && (p = Py_GETENV("PYTHONNOUSERSITE")) && *p != '\0') Py_NoUserSiteDirectory = 1; if ((p = Py_GETENV("PYTHONWARNINGS")) && *p != '\0') { char *buf, *warning; buf = (char *)malloc(strlen(p) + 1); if (buf == NULL) Py_FatalError( "not enough memory to copy PYTHONWARNINGS"); strcpy(buf, p); for (warning = strtok(buf, ","); warning != NULL; warning = strtok(NULL, ",")) PySys_AddWarnOption(warning); free(buf); } if (command == NULL && module == NULL && _PyOS_optind < argc && strcmp(argv[_PyOS_optind], "-") != 0) { #ifdef __VMS filename = decc$translate_vms(argv[_PyOS_optind]); if (filename == (char *)0 || filename == (char *)-1) filename = argv[_PyOS_optind]; #else filename = argv[_PyOS_optind]; #endif } stdin_is_interactive = Py_FdIsInteractive(stdin, (char *)0); if (unbuffered) { #if defined(MS_WINDOWS) || defined(__CYGWIN__) _setmode(fileno(stdin), O_BINARY); _setmode(fileno(stdout), O_BINARY); #endif #ifdef HAVE_SETVBUF setvbuf(stdin, (char *)NULL, _IONBF, BUFSIZ); setvbuf(stdout, (char *)NULL, _IONBF, BUFSIZ); setvbuf(stderr, (char *)NULL, _IONBF, BUFSIZ); #else /* !HAVE_SETVBUF */ setbuf(stdin, (char *)NULL); setbuf(stdout, (char *)NULL); setbuf(stderr, (char *)NULL); #endif /* !HAVE_SETVBUF */ } else if (Py_InteractiveFlag) { #ifdef MS_WINDOWS /* Doesn't have to have line-buffered -- use unbuffered */ /* Any set[v]buf(stdin, ...) screws up Tkinter :-( */ setvbuf(stdout, (char *)NULL, _IONBF, BUFSIZ); #else /* !MS_WINDOWS */ #ifdef HAVE_SETVBUF setvbuf(stdin, (char *)NULL, _IOLBF, BUFSIZ); setvbuf(stdout, (char *)NULL, _IOLBF, BUFSIZ); #endif /* HAVE_SETVBUF */ #endif /* !MS_WINDOWS */ /* Leave stderr alone - it should be unbuffered anyway. */ } #ifdef __VMS else { setvbuf (stdout, (char *)NULL, _IOLBF, BUFSIZ); } #endif /* __VMS */ #ifdef __APPLE__ /* On MacOS X, when the Python interpreter is embedded in an application bundle, it gets executed by a bootstrapping script that does os.execve() with an argv[0] that's different from the actual Python executable. This is needed to keep the Finder happy, or rather, to work around Apple's overly strict requirements of the process name. However, we still need a usable sys.executable, so the actual executable path is passed in an environment variable. See Lib/plat-mac/bundlebuiler.py for details about the bootstrap script. */ if ((p = Py_GETENV("PYTHONEXECUTABLE")) && *p != '\0') Py_SetProgramName(p); else Py_SetProgramName(argv[0]); #else Py_SetProgramName(argv[0]); #endif Py_Initialize(); if (Py_VerboseFlag || (command == NULL && filename == NULL && module == NULL && stdin_is_interactive)) { fprintf(stderr, "Python %s on %s\n", Py_GetVersion(), Py_GetPlatform()); if (!Py_NoSiteFlag) fprintf(stderr, "%s\n", COPYRIGHT); } if (command != NULL) { /* Backup _PyOS_optind and force sys.argv[0] = '-c' */ _PyOS_optind--; argv[_PyOS_optind] = "-c"; } if (module != NULL) { /* Backup _PyOS_optind and force sys.argv[0] = '-c' so that PySys_SetArgv correctly sets sys.path[0] to '' rather than looking for a file called "-m". See tracker issue #8202 for details. */ _PyOS_optind--; argv[_PyOS_optind] = "-c"; } PySys_SetArgv(argc-_PyOS_optind, argv+_PyOS_optind); if ((Py_InspectFlag || (command == NULL && filename == NULL && module == NULL)) && isatty(fileno(stdin))) { PyObject *v; v = PyImport_ImportModule("readline"); if (v == NULL) PyErr_Clear(); else Py_DECREF(v); } if (command) { sts = PyRun_SimpleStringFlags(command, &cf) != 0; free(command); } else if (module) { sts = RunModule(module, 1); free(module); } else { if (filename == NULL && stdin_is_interactive) { Py_InspectFlag = 0; /* do exit on SystemExit */ RunStartupFile(&cf); } /* XXX */ sts = -1; /* keep track of whether we've already run __main__ */ if (filename != NULL) { sts = RunMainFromImporter(filename); } if (sts==-1 && filename!=NULL) { if ((fp = fopen(filename, "r")) == NULL) { fprintf(stderr, "%s: can't open file '%s': [Errno %d] %s\n", argv[0], filename, errno, strerror(errno)); return 2; } else if (skipfirstline) { int ch; /* Push back first newline so line numbers remain the same */ while ((ch = getc(fp)) != EOF) { if (ch == '\n') { (void)ungetc(ch, fp); break; } } } { /* XXX: does this work on Win/Win64? (see posix_fstat) */ struct stat sb; if (fstat(fileno(fp), &sb) == 0 && S_ISDIR(sb.st_mode)) { fprintf(stderr, "%s: '%s' is a directory, cannot continue\n", argv[0], filename); fclose(fp); return 1; } } } if (sts==-1) { /* call pending calls like signal handlers (SIGINT) */ if (Py_MakePendingCalls() == -1) { PyErr_Print(); sts = 1; } else { sts = PyRun_AnyFileExFlags( fp, filename == NULL ? "<stdin>" : filename, filename != NULL, &cf) != 0; } } } /* Check this environment variable at the end, to give programs the * opportunity to set it from Python. */ if (!Py_InspectFlag && (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') { Py_InspectFlag = 1; } if (Py_InspectFlag && stdin_is_interactive && (filename != NULL || command != NULL || module != NULL)) { Py_InspectFlag = 0; /* XXX */ sts = PyRun_AnyFileFlags(stdin, "<stdin>", &cf) != 0; } Py_Finalize(); #ifdef RISCOS if (Py_RISCOSWimpFlag) fprintf(stderr, "\x0cq\x0c"); /* make frontend quit */ #endif #ifdef __INSURE__ /* Insure++ is a memory analysis tool that aids in discovering * memory leaks and other memory problems. On Python exit, the * interned string dictionary is flagged as being in use at exit * (which it is). Under normal circumstances, this is fine because * the memory will be automatically reclaimed by the system. Under * memory debugging, it's a huge source of useless noise, so we * trade off slower shutdown for less distraction in the memory * reports. -baw */ _Py_ReleaseInternedStrings(); #endif /* __INSURE__ */ return sts; } Good God Almighty...it is big enough to sink the Titanic. It seems as though Python did the "Intro to Programming 101" trick and just moved all of main()'s code to a different function called it something very similar to "main". Here's my question: Is this code terribly written, or are there other reasons reasons to have a short main function? As it stands right now, I see absolutely no difference between doing this and just moving the code in Py_Main() back into main(). Am I wrong in thinking this?

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• Why should main() be short?

  - by Stargazer712

  I've been programming for over 9 years, and according to the advice of my first programming teacher, I always keep my main() function extremely short. At first I had no idea why. I just obeyed without understanding, much to the delight of my professors. After gaining experience, I realized that if I designed my code correctly, having a short main() function just sortof happened. Writing modularized code and following the single responsibility principle allowed my code to be designed in "bunches", and main() served as nothing more than a catalyst to get the program running. Fast forward to a few weeks ago, I was looking at Python's souce code, and I found the main() function: /* Minimal main program -- everything is loaded from the library */ ... int main(int argc, char **argv) { ... return Py_Main(argc, argv); } Yay python. Short main() function == Good code. Programming teachers were right. Wanting to look deeper, I took a look at Py_Main. In its entirety, it is defined as follows: /* Main program */ int Py_Main(int argc, char **argv) { int c; int sts; char *command = NULL; char *filename = NULL; char *module = NULL; FILE *fp = stdin; char *p; int unbuffered = 0; int skipfirstline = 0; int stdin_is_interactive = 0; int help = 0; int version = 0; int saw_unbuffered_flag = 0; PyCompilerFlags cf; cf.cf_flags = 0; orig_argc = argc; /* For Py_GetArgcArgv() */ orig_argv = argv; #ifdef RISCOS Py_RISCOSWimpFlag = 0; #endif PySys_ResetWarnOptions(); while ((c = _PyOS_GetOpt(argc, argv, PROGRAM_OPTS)) != EOF) { if (c == 'c') { /* -c is the last option; following arguments that look like options are left for the command to interpret. */ command = (char *)malloc(strlen(_PyOS_optarg) + 2); if (command == NULL) Py_FatalError( "not enough memory to copy -c argument"); strcpy(command, _PyOS_optarg); strcat(command, "\n"); break; } if (c == 'm') { /* -m is the last option; following arguments that look like options are left for the module to interpret. */ module = (char *)malloc(strlen(_PyOS_optarg) + 2); if (module == NULL) Py_FatalError( "not enough memory to copy -m argument"); strcpy(module, _PyOS_optarg); break; } switch (c) { case 'b': Py_BytesWarningFlag++; break; case 'd': Py_DebugFlag++; break; case '3': Py_Py3kWarningFlag++; if (!Py_DivisionWarningFlag) Py_DivisionWarningFlag = 1; break; case 'Q': if (strcmp(_PyOS_optarg, "old") == 0) { Py_DivisionWarningFlag = 0; break; } if (strcmp(_PyOS_optarg, "warn") == 0) { Py_DivisionWarningFlag = 1; break; } if (strcmp(_PyOS_optarg, "warnall") == 0) { Py_DivisionWarningFlag = 2; break; } if (strcmp(_PyOS_optarg, "new") == 0) { /* This only affects __main__ */ cf.cf_flags |= CO_FUTURE_DIVISION; /* And this tells the eval loop to treat BINARY_DIVIDE as BINARY_TRUE_DIVIDE */ _Py_QnewFlag = 1; break; } fprintf(stderr, "-Q option should be `-Qold', " "`-Qwarn', `-Qwarnall', or `-Qnew' only\n"); return usage(2, argv[0]); /* NOTREACHED */ case 'i': Py_InspectFlag++; Py_InteractiveFlag++; break; /* case 'J': reserved for Jython */ case 'O': Py_OptimizeFlag++; break; case 'B': Py_DontWriteBytecodeFlag++; break; case 's': Py_NoUserSiteDirectory++; break; case 'S': Py_NoSiteFlag++; break; case 'E': Py_IgnoreEnvironmentFlag++; break; case 't': Py_TabcheckFlag++; break; case 'u': unbuffered++; saw_unbuffered_flag = 1; break; case 'v': Py_VerboseFlag++; break; #ifdef RISCOS case 'w': Py_RISCOSWimpFlag = 1; break; #endif case 'x': skipfirstline = 1; break; /* case 'X': reserved for implementation-specific arguments */ case 'U': Py_UnicodeFlag++; break; case 'h': case '?': help++; break; case 'V': version++; break; case 'W': PySys_AddWarnOption(_PyOS_optarg); break; /* This space reserved for other options */ default: return usage(2, argv[0]); /*NOTREACHED*/ } } if (help) return usage(0, argv[0]); if (version) { fprintf(stderr, "Python %s\n", PY_VERSION); return 0; } if (Py_Py3kWarningFlag && !Py_TabcheckFlag) /* -3 implies -t (but not -tt) */ Py_TabcheckFlag = 1; if (!Py_InspectFlag && (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') Py_InspectFlag = 1; if (!saw_unbuffered_flag && (p = Py_GETENV("PYTHONUNBUFFERED")) && *p != '\0') unbuffered = 1; if (!Py_NoUserSiteDirectory && (p = Py_GETENV("PYTHONNOUSERSITE")) && *p != '\0') Py_NoUserSiteDirectory = 1; if ((p = Py_GETENV("PYTHONWARNINGS")) && *p != '\0') { char *buf, *warning; buf = (char *)malloc(strlen(p) + 1); if (buf == NULL) Py_FatalError( "not enough memory to copy PYTHONWARNINGS"); strcpy(buf, p); for (warning = strtok(buf, ","); warning != NULL; warning = strtok(NULL, ",")) PySys_AddWarnOption(warning); free(buf); } if (command == NULL && module == NULL && _PyOS_optind < argc && strcmp(argv[_PyOS_optind], "-") != 0) { #ifdef __VMS filename = decc$translate_vms(argv[_PyOS_optind]); if (filename == (char *)0 || filename == (char *)-1) filename = argv[_PyOS_optind]; #else filename = argv[_PyOS_optind]; #endif } stdin_is_interactive = Py_FdIsInteractive(stdin, (char *)0); if (unbuffered) { #if defined(MS_WINDOWS) || defined(__CYGWIN__) _setmode(fileno(stdin), O_BINARY); _setmode(fileno(stdout), O_BINARY); #endif #ifdef HAVE_SETVBUF setvbuf(stdin, (char *)NULL, _IONBF, BUFSIZ); setvbuf(stdout, (char *)NULL, _IONBF, BUFSIZ); setvbuf(stderr, (char *)NULL, _IONBF, BUFSIZ); #else /* !HAVE_SETVBUF */ setbuf(stdin, (char *)NULL); setbuf(stdout, (char *)NULL); setbuf(stderr, (char *)NULL); #endif /* !HAVE_SETVBUF */ } else if (Py_InteractiveFlag) { #ifdef MS_WINDOWS /* Doesn't have to have line-buffered -- use unbuffered */ /* Any set[v]buf(stdin, ...) screws up Tkinter :-( */ setvbuf(stdout, (char *)NULL, _IONBF, BUFSIZ); #else /* !MS_WINDOWS */ #ifdef HAVE_SETVBUF setvbuf(stdin, (char *)NULL, _IOLBF, BUFSIZ); setvbuf(stdout, (char *)NULL, _IOLBF, BUFSIZ); #endif /* HAVE_SETVBUF */ #endif /* !MS_WINDOWS */ /* Leave stderr alone - it should be unbuffered anyway. */ } #ifdef __VMS else { setvbuf (stdout, (char *)NULL, _IOLBF, BUFSIZ); } #endif /* __VMS */ #ifdef __APPLE__ /* On MacOS X, when the Python interpreter is embedded in an application bundle, it gets executed by a bootstrapping script that does os.execve() with an argv[0] that's different from the actual Python executable. This is needed to keep the Finder happy, or rather, to work around Apple's overly strict requirements of the process name. However, we still need a usable sys.executable, so the actual executable path is passed in an environment variable. See Lib/plat-mac/bundlebuiler.py for details about the bootstrap script. */ if ((p = Py_GETENV("PYTHONEXECUTABLE")) && *p != '\0') Py_SetProgramName(p); else Py_SetProgramName(argv[0]); #else Py_SetProgramName(argv[0]); #endif Py_Initialize(); if (Py_VerboseFlag || (command == NULL && filename == NULL && module == NULL && stdin_is_interactive)) { fprintf(stderr, "Python %s on %s\n", Py_GetVersion(), Py_GetPlatform()); if (!Py_NoSiteFlag) fprintf(stderr, "%s\n", COPYRIGHT); } if (command != NULL) { /* Backup _PyOS_optind and force sys.argv[0] = '-c' */ _PyOS_optind--; argv[_PyOS_optind] = "-c"; } if (module != NULL) { /* Backup _PyOS_optind and force sys.argv[0] = '-c' so that PySys_SetArgv correctly sets sys.path[0] to '' rather than looking for a file called "-m". See tracker issue #8202 for details. */ _PyOS_optind--; argv[_PyOS_optind] = "-c"; } PySys_SetArgv(argc-_PyOS_optind, argv+_PyOS_optind); if ((Py_InspectFlag || (command == NULL && filename == NULL && module == NULL)) && isatty(fileno(stdin))) { PyObject *v; v = PyImport_ImportModule("readline"); if (v == NULL) PyErr_Clear(); else Py_DECREF(v); } if (command) { sts = PyRun_SimpleStringFlags(command, &cf) != 0; free(command); } else if (module) { sts = RunModule(module, 1); free(module); } else { if (filename == NULL && stdin_is_interactive) { Py_InspectFlag = 0; /* do exit on SystemExit */ RunStartupFile(&cf); } /* XXX */ sts = -1; /* keep track of whether we've already run __main__ */ if (filename != NULL) { sts = RunMainFromImporter(filename); } if (sts==-1 && filename!=NULL) { if ((fp = fopen(filename, "r")) == NULL) { fprintf(stderr, "%s: can't open file '%s': [Errno %d] %s\n", argv[0], filename, errno, strerror(errno)); return 2; } else if (skipfirstline) { int ch; /* Push back first newline so line numbers remain the same */ while ((ch = getc(fp)) != EOF) { if (ch == '\n') { (void)ungetc(ch, fp); break; } } } { /* XXX: does this work on Win/Win64? (see posix_fstat) */ struct stat sb; if (fstat(fileno(fp), &sb) == 0 && S_ISDIR(sb.st_mode)) { fprintf(stderr, "%s: '%s' is a directory, cannot continue\n", argv[0], filename); fclose(fp); return 1; } } } if (sts==-1) { /* call pending calls like signal handlers (SIGINT) */ if (Py_MakePendingCalls() == -1) { PyErr_Print(); sts = 1; } else { sts = PyRun_AnyFileExFlags( fp, filename == NULL ? "<stdin>" : filename, filename != NULL, &cf) != 0; } } } /* Check this environment variable at the end, to give programs the * opportunity to set it from Python. */ if (!Py_InspectFlag && (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') { Py_InspectFlag = 1; } if (Py_InspectFlag && stdin_is_interactive && (filename != NULL || command != NULL || module != NULL)) { Py_InspectFlag = 0; /* XXX */ sts = PyRun_AnyFileFlags(stdin, "<stdin>", &cf) != 0; } Py_Finalize(); #ifdef RISCOS if (Py_RISCOSWimpFlag) fprintf(stderr, "\x0cq\x0c"); /* make frontend quit */ #endif #ifdef __INSURE__ /* Insure++ is a memory analysis tool that aids in discovering * memory leaks and other memory problems. On Python exit, the * interned string dictionary is flagged as being in use at exit * (which it is). Under normal circumstances, this is fine because * the memory will be automatically reclaimed by the system. Under * memory debugging, it's a huge source of useless noise, so we * trade off slower shutdown for less distraction in the memory * reports. -baw */ _Py_ReleaseInternedStrings(); #endif /* __INSURE__ */ return sts; } Good God Almighty...it is big enough to sink the Titanic. It seems as though Python did the "Intro to Programming 101" trick and just moved all of main()'s code to a different function called it something very similar to "main". Here's my question: Is this code terribly written, or are there other reasons to have a short main function? As it stands right now, I see absolutely no difference between doing this and just moving the code in Py_Main() back into main(). Am I wrong in thinking this?

  Read the article

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