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  • Simple binary File I/O problem with cstdio(c++)

    - by Atilla Filiz
    The c++ program below fails to read the file. I know using cstdio is not good practice but that what I am used to and it should work anyway. $ ls -l l.uyvy -rw-r--r-- 1 atilla atilla 614400 2010-04-24 18:11 l.uyvy $ ./a.out l.uyvy Read 0 bytes out of 614400, possibly wrong file code: #include<cstdio> int main(int argc, char* argv[]) { FILE *fp; if(argc<2) { printf("usage: %s <input>\n",argv[0]); return 1; } fp=fopen(argv[1],"rb"); if(!fp) { printf("erör, cannot open %s for reading\n",argv[1]); return -1; } int bytes_read=fread(imgdata,1,2*IMAGE_SIZE,fp); //2bytes per pixel fclose(fp); if(bytes_read < 2*IMAGE_SIZE) { printf("Read %d bytes out of %d, possibly wrong file\n", bytes_read, 2*IMAGE_SIZE); return -1; } return 0; }

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  • Lots of questions about file I/O (reading/writing message strings)

    - by Nazgulled
    Hi, For this university project I'm doing (for which I've made a couple of posts in the past), which is some sort of social network, it's required the ability for the users to exchange messages. At first, I designed my data structures to hold ALL messages in a linked list, limiting the message size to 256 chars. However, I think my instructors will prefer if I save the messages on disk and read them only when I need them. Of course, they won't say what they prefer, I need to make a choice and justify the best I can why I went that route. One thing to keep in mind is that I only need to save the latest 20 messages from each user, no more. Right now I have an Hash Table that will act as inbox, this will be inside the user profile. This Hash Table will be indexed by name (the user that sent the message). The value for each element will be a data structure holding an array of size_t with 20 elements (20 messages like I said above). The idea is to keep track of the disk file offsets and bytes written. Then, when I need to read a message, I just need to use fseek() and read the necessary bytes. I think this could work nicely... I could use just one single file to hold all messages from all users in the network. I'm saying one single file because a colleague asked an instructor about saving the messages from each user independently which he replied that it might not be the best approach cause the file system has it's limits. That's why I'm thinking of going the single file route. However, this presents a problem... Since I only need to save the latest 20 messages, I need to discard the older ones when I reach this limit. I have no idea how to do this... All I know is about fread() and fwrite() to read/write bytes from/to files. How can I go to a file offset and say "hey, delete the following X bytes"? Even if I could do that, there's another problem... All offsets below that one will be completely different and I would have to process all users mailboxes to fix the problem. Which would be a pain... So, any suggestions to solve my problems? What do you suggest?

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  • Read variable-length records from a buffer - weird memory issues

    - by bsg
    Hi, I'm trying to implement an i/o intensive quicksort (C++ qsort) on a very large dataset. In the interests of speed, I'd like to read in a chunk of data at a time into a buffer and then use qsort to sort it inside the buffer. (I am currently working with text files but would like to move to binary soon.) However, my data is composed of variable-length records, and qsort needs to be told the length of the record in order to sort. Is there any way to standardize this? The only thing I could think of was rather convoluted: my program currently reads from the buffer until it hits a linefeed character ('10' in ascii), transferring each character over to another array. When it finds a linefeed (the delimiter in the input file), it fills the number of spaces remaining in the buffer for that record (record size is set to 30) with null characters. This way, I should end up with a buffer full of fixed-size records to give qsort. I know there are several problems with my approach, one being that it's just clumsy, another that the record size might conceivably be larger than 30, but is generally much less. Is there a better way of doing this? As well, my current code doesn't even work. When I debug it, it seems to be transferring characters from one buffer to the other, but when I try to print out the buffer, it contains only the first record. Here is my code: FILE *fp; unsigned char *buff; unsigned char *realbuff; FILE *inputFiles[NUM_INPUT_FILES]; buff = (unsigned char *) malloc(2048); realbuff = (unsigned char *) malloc(NUM_RECORDS * RECORD_SIZE); fp = fopen("postings0.txt", "r"); if(fp) { fread(buff, 1, 2048, fp); /*for(int i=0; i <30; i++) cout << buff[i] <<endl;*/ int y=0; int recordcounter = 0; //cout << buff; for(int i=0;i <100; i++) { if(buff[i] != char(10)) { realbuff[y] = buff[i]; y++; recordcounter++; } else { if(recordcounter < RECORD_SIZE) for(int j=recordcounter; j < RECORD_SIZE;j++) { realbuff[y] = char(0); y++; } recordcounter = 0; } } cout << realbuff <<endl; cout << buff; } else cout << "sorry"; Thank you very much, bsg

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  • File counter adds 2 instead of 1

    - by Derk
    I made a simple counter, but it increments by 2 instead of 1. $handle = fopen('progress.txt', 'r'); $pro = fgets($handle); print $pro; // incremented by 2, WTF? fclose($handle); $handle = fopen('progress.txt', 'w'); fwrite($handle, $pro); fclose($handle); Everytime I read the file it has been incremented by 2, instead of 1.

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  • Server-environment and configuration: How bad is fread() etc?

    - by zero
    Hello dear commmunity, good day! I run a little site (now for several months ) that has users accessing big files, for download as well for streaming to the browser. It's fairly active, so assuming the worst, how bad is getting php to read the files that would be stored outside of the webroot and then getting it to echo it to a page dynamically for the browser to then read? My question is: how bad is fread() etc in this context!? zero

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  • How to display the found matches of preg_match function in PHP?

    - by Eric
    I am using the following to check if links exist on file.php: $fopen = fopen('file.php', 'r'); $fread = fread($fopen, filesize('file.php')); $pattern = "/^<a href=/i"; if (preg_match($pattern, $fread)) { echo 'Match Found'; } else { echo 'Match Not Found'; } if I echo preg_match($pattern, $fread) I get a boolean value, not the found matches. I tried what was on the php.net manual and did this: preg_match($pattern, $fread, $matches); then when I echoed $matches I got "Array" message. So I tried a foreach loop and when that didn't display anything I tried $matches[0] and that too outputted nothing. So how does one go about displaying the matches found?

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  • How to solve this simple PHP forloop issue?

    - by Londonbroil Wellington
    Here is the content of my flat file database: Jacob | Little | 22 | Male | Web Developer * Adam | Johnson | 45 | Male | President * Here is my php code: <?php $fopen = fopen('db.txt', 'r'); if (!$fopen) { echo 'File not found'; } $fread = fread($fopen, filesize('db.txt')); $records = explode('|', $fread); ?> <table border="1" width="100%"> <tr> <thead> <th>First Name</th> <th>Last Name</th> <th>Age</th> <th>Sex</th> <th>Occupation</th> </thead> </tr> <?php $rows = explode('*', $fread); for($i = 0; $i < count($rows) - 1; $i++) { echo '<tr>'; echo '<td>'.$records[0].'</td>'; echo '<td>'.$records[1].'</td>'; echo '<td>'.$records[2].'</td>'; echo '<td>'.$records[3].'</td>'; echo '<td>'.$records[4].'</td>'; echo '</tr>'; } fclose($fopen); ?> </table> Problem is I am getting the output of the first record repeated twice instead of 2 records one for Jacob and one for Adam. How to fix this?

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  • How to read integer in Erlang?

    - by Jace Jung
    I'm trying to read user input of integer. (like cin nInput; in C++) I found io:fread bif from http://www.erlang.org/doc/man/io.html, so I write code like this. {ok, X} = io:fread("input : ", "~d"), io:format("~p~n", [X]). but when I input 10, the erlang terminal keep giving me "\n" not 10. I assume fread automatically read 10 and conert this into string. How can I read integer value directly? Is there any way to do this? Thank you for reading this.

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  • Why fgetc too slow?

    - by user14284
    I've written a program that reads an whole file via fgetc: while ((c = fgetc(f)) != EOF) { ... } But the program is too slow. When I changed fgetc to fread, static unsigned char buf[4096]; while ((n = fread(buf, 1, sizeof(buf), f)) > 0) { ... } the program works about 10 times faster. Why? As I know, fgetc is a buffered function, so it should work as fast as the second version with explicit buffer, isn't it?

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  • Fastest file reading in C.

    - by Jay
    Right now I am using fread() to read a file, but in other language fread() is inefficient i'v been told. Is this the same in C? If so, how would faster file reading be done?

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  • Execute SSH commands on Cisco router. Codeigniter SSH library

    - by jomajo
    I have a little problem. I'm using Codeigniter with SSH library written by Shuky (https://bitbucket.org/quicktips/codeigniter-ssh2-library/src/a444968345ba/SSH.php -- You can see the code by following this link). Everything related with SSH works fine with other devices, but when I try to use this library and execute commands on Cisco devices, nothing happens (commands are not executed). I know that the connection is successful, but I can't execute any commands. When I try to run and execute comands through SSH on Cisco devices I get this error: A PHP Error was encountered Severity: Warning Message: stream_set_blocking() expects parameter 1 to be resource, boolean given Filename: libraries/SSH.php Line Number: 128 A PHP Error was encountered Severity: Warning Message: fread() expects parameter 1 to be resource, boolean given Filename: libraries/SSH.php Line Number: 129 In the library these lines look like this: /** * Get stream data * * @access privte * @return bool */ function _get_stream_data($stream) { stream_set_blocking( $stream, true ); while( $buf = fread($stream,4096) ) { $this->data .= $buf.'~'; } return TRUE; } line 128 - stream_set_blocking( $stream, true ); line 129 - while( $buf = fread($stream,4096) ) { Maybe you guys know where the problem is? Thank you for your time and your answers!

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  • Convert Bitmap Files into JPEG using the GD library in PHP

    - by Daniel P
    I have been trying to figure out a way to convert bitmap files into a JPEG using the GD library in PHP. I have tried numerous implementations but nothing seems to work. I have tried to tell my client that they should not use Bitmap files but he insists and quite frankly does not comprehend enough about computers to convert them to JPG on his own. I can not use ImageMagick on this server and I need a pure GD solution. Thank you in advance for any and all help. EDIT: The bitmap images that are being used are 16-bit and that is where the problem is occurring. I have this function that I have working .... kinda: function ImageCreateFromBMP($filename) { if (! $f1 = fopen($filename,"rb")) return FALSE; $FILE = unpack("vfile_type/Vfile_size/Vreserved/Vbitmap_offset", fread($f1,14)); if ($FILE['file_type'] != 19778) return FALSE; $BMP = unpack('Vheader_size/Vwidth/Vheight/vplanes/vbits_per_pixel'. '/Vcompression/Vsize_bitmap/Vhoriz_resolution'. '/Vvert_resolution/Vcolors_used/Vcolors_important', fread($f1,40)); $BMP['colors'] = pow(2,$BMP['bits_per_pixel']); if ($BMP['size_bitmap'] == 0) $BMP['size_bitmap'] = $FILE['file_size'] - $FILE['bitmap_offset']; $BMP['bytes_per_pixel'] = $BMP['bits_per_pixel']/8; $BMP['bytes_per_pixel2'] = ceil($BMP['bytes_per_pixel']); $BMP['decal'] = ($BMP['width']*$BMP['bytes_per_pixel']/4); $BMP['decal'] -= floor($BMP['width']*$BMP['bytes_per_pixel']/4); $BMP['decal'] = 4-(4*$BMP['decal']); if ($BMP['decal'] == 4) $BMP['decal'] = 0; $PALETTE = array(); if ($BMP['colors'] < 16777216 && $BMP['colors'] != 65536) { $PALETTE = unpack('V'.$BMP['colors'], fread($f1,$BMP['colors']*4)); } $IMG = fread($f1,$BMP['size_bitmap']); $VIDE = chr(0); $res = imagecreatetruecolor($BMP['width'],$BMP['height']); $P = 0; $Y = $BMP['height']-1; while ($Y >= 0) { $X=0; while ($X < $BMP['width']) { if ($BMP['bits_per_pixel'] == 24) $COLOR = unpack("V",substr($IMG,$P,3).$VIDE); elseif ($BMP['bits_per_pixel'] == 16) { $COLOR = unpack("v",substr($IMG,$P,2)); $blue = ($COLOR[1] & 0x001f) << 3; $green = ($COLOR[1] & 0x07e0) >> 3; $red = ($COLOR[1] & 0xf800) >> 8; $COLOR[1] = $red * 65536 + $green * 256 + $blue; } elseif ($BMP['bits_per_pixel'] == 8) { $COLOR = unpack("n",$VIDE.substr($IMG,$P,1)); $COLOR[1] = $PALETTE[$COLOR[1]+1]; } elseif ($BMP['bits_per_pixel'] == 4) { $COLOR = unpack("n",$VIDE.substr($IMG,floor($P),1)); if (($P*2)%2 == 0) $COLOR[1] = ($COLOR[1] >> 4) ; else $COLOR[1] = ($COLOR[1] & 0x0F); $COLOR[1] = $PALETTE[$COLOR[1]+1]; } elseif ($BMP['bits_per_pixel'] == 1) { $COLOR = unpack("n",$VIDE.substr($IMG,floor($P),1)); if (($P*8)%8 == 0) $COLOR[1] = $COLOR[1] >>7; elseif (($P*8)%8 == 1) $COLOR[1] = ($COLOR[1] & 0x40)>>6; elseif (($P*8)%8 == 2) $COLOR[1] = ($COLOR[1] & 0x20)>>5; elseif (($P*8)%8 == 3) $COLOR[1] = ($COLOR[1] & 0x10)>>4; elseif (($P*8)%8 == 4) $COLOR[1] = ($COLOR[1] & 0x8)>>3; elseif (($P*8)%8 == 5) $COLOR[1] = ($COLOR[1] & 0x4)>>2; elseif (($P*8)%8 == 6) $COLOR[1] = ($COLOR[1] & 0x2)>>1; elseif (($P*8)%8 == 7) $COLOR[1] = ($COLOR[1] & 0x1); $COLOR[1] = $PALETTE[$COLOR[1]+1]; } else return FALSE; imagesetpixel($res,$X,$Y,$COLOR[1]); $X++; $P += $BMP['bytes_per_pixel']; } $Y--; $P+=$BMP['decal']; } fclose($f1); return $res; } The resulting image is this: If you look at the image on the left hand side you can see that the resulting image is not correctly lined up. The little sliver belongs on the right hand side. Where is the code going wrong? The problem is occurring in the 16-bit else-if. Thank you again for all the help.

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  • File IO, Handling CRLF

    - by aCuria
    Hi, i am writing a program that takes a file and splits it up into multiple small files of a user specified size, then join the multiple small files back again. 1) the code must work for c, c++ 2) i am compiling with multiple compilers. I am reading and writing to the files by using the stl functions fread() and fwrite() The problem I am having pertains to CRLF. If the file I am reading from contains CRLF, then I want to retain it when i split and join the files back together. If the file contains LF, then i want to retain LF. Unfortunately, fread() seems to store CRLF as \n (I think), and whatever is written by fwrite() is compiler-dependent. How do i approach this problem? Thanks.

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  • posting php code using jquery .html()

    - by Emmanuel Imwene
    simple query,but it's giving me a headache, i need a division to be updated with a changed session variable each time a user clicks on a name,i figured i'd use .html() using jquery to update the division, i don't know if you can do this, but here goes: $("#inner").html('<?php session_start(); if(file_exists($_SESSION['full'])||file_exists($_SESSION['str'])){ if(file_exists($_SESSION['full'])) { $full=$_SESSION['full']; $handlle = fopen($full, "r"); $contents = fread($handlle, filesize($full)); fclose($handlle); echo $contents; echo '<script type="text/javascript" src="jquery-1.8.0.min (1).js">'; echo '</script>'; echo '<script type="text/javascript">'; echo 'function loadLog(){ var oldscrollHeight = $("#inner").attr("scrollHeight") - 20; $.ajax({ url: \''.$_SESSION['full'].'\', cache: false, success: function(html){ $("#inner").html(html); //Insert chat log into the #chatbox div var newscrollHeight = $("#inner").attr("scrollHeight") - 20; if(newscrollHeight > oldscrollHeight){ $("#inner").animate({ scrollTop: newscrollHeight }, \'normal\'); //Autoscroll to bottom of div } }, }); } setInterval (loadLog, 2500);'; echo '</script>'; } else { $str=$_SESSION['str']; if(file_exists($str)) { $handle = fopen($str, 'r'); $contents = fread($handle, filesize($str)); fclose($handle); echo $contents; $full=$_SESSION['full']; $handlle = fopen($full, "r"); $contents = fread($handlle, filesize($full)); fclose($handlle); echo $contents; echo '<script type="text/javascript" src="jquery-1.8.0.min (1).js">'; echo '</script>'; echo '<script type="text/javascript">'; echo 'function loadLog(){ var oldscrollHeight = $("#inner").attr("scrollHeight") - 20; $.ajax({ url: \''.$_SESSION['str'].'\', cache: false, success: function(html){ $("#inner").html(html); //Insert chat log into the #chatbox div var newscrollHeight = $("#inner").attr("scrollHeight") - 20; if(newscrollHeight > oldscrollHeight){ $("#inner").animate({ scrollTop: newscrollHeight }, \'normal\'); //Autoscroll to bottom of div } }, }); } setInterval (loadLog, 2500);'; echo '</script>'; } } } ?>'); is that legal, if not, how would i accomplish this?

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  • C read part of file into cache

    - by Pete Jodo
    I have to do a program (for Linux) where there's an extremely large index file and I have to search and interpret the data from the file. Now the catch is, I'm only allowed to have x-bytes of the file cached at any time (determined by argument) so I have to remove certain data from the cache if it's not what I'm looking for. If my understanding is correct, fopen (r) doesn't put anything in the cache, only when I call getc or fread(specifying size) does it get cached. So my question is, lets say I use fread and read 100 bytes but after checking it, only 20 of the 100 bytes contains the data I need; how would I remove the useless 80 bytes from cache (or overwrite it) in order to read more from the file.

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  • Pointers in C with binary file

    - by darkie15
    Hi All, I am reading the contents of the file using fread into an char array. But I am not sure why it is not getting printed in the output. Here is the code: void getInfo(FILE* inputFile) { char chunk[4]; int liIndex; for (liIndex = 0 ; liIndex < 4 ; liIndex++) { fread(chunk, sizeof(char), 4, inputFile); } printf("\n chunk %s", chunk); } Output prints nothing at all. Where am I going wrong? Regards , darkie

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  • processing an audio wav file with C

    - by sa125
    Hi - I'm working on processing the amplitude of a wav file and scaling it by some decimal factor. I'm trying to wrap my head around how to read and re-write the file in a memory-efficient way while also trying to tackle the nuances of the language (I'm new to C). The file can be in either an 8- or 16-bit format. The way I thought of doing this is by first reading the header data into some pre-defined struct, and then processing the actual data in a loop where I'll read a chunk of data into a buffer, do whatever is needed to it, and then write it to the output. #include <stdio.h> #include <stdlib.h> typedef struct header { char chunk_id[4]; int chunk_size; char format[4]; char subchunk1_id[4]; int subchunk1_size; short int audio_format; short int num_channels; int sample_rate; int byte_rate; short int block_align; short int bits_per_sample; short int extra_param_size; char subchunk2_id[4]; int subchunk2_size; } header; typedef struct header* header_p; void scale_wav_file(char * input, float factor, int is_8bit) { FILE * infile = fopen(input, "rb"); FILE * outfile = fopen("outfile.wav", "wb"); int BUFSIZE = 4000, i, MAX_8BIT_AMP = 255, MAX_16BIT_AMP = 32678; // used for processing 8-bit file unsigned char inbuff8[BUFSIZE], outbuff8[BUFSIZE]; // used for processing 16-bit file short int inbuff16[BUFSIZE], outbuff16[BUFSIZE]; // header_p points to a header struct that contains the file's metadata fields header_p meta = (header_p)malloc(sizeof(header)); if (infile) { // read and write header data fread(meta, 1, sizeof(header), infile); fwrite(meta, 1, sizeof(meta), outfile); while (!feof(infile)) { if (is_8bit) { fread(inbuff8, 1, BUFSIZE, infile); } else { fread(inbuff16, 1, BUFSIZE, infile); } // scale amplitude for 8/16 bits for (i=0; i < BUFSIZE; ++i) { if (is_8bit) { outbuff8[i] = factor * inbuff8[i]; if ((int)outbuff8[i] > MAX_8BIT_AMP) { outbuff8[i] = MAX_8BIT_AMP; } } else { outbuff16[i] = factor * inbuff16[i]; if ((int)outbuff16[i] > MAX_16BIT_AMP) { outbuff16[i] = MAX_16BIT_AMP; } else if ((int)outbuff16[i] < -MAX_16BIT_AMP) { outbuff16[i] = -MAX_16BIT_AMP; } } } // write to output file for 8/16 bit if (is_8bit) { fwrite(outbuff8, 1, BUFSIZE, outfile); } else { fwrite(outbuff16, 1, BUFSIZE, outfile); } } } // cleanup if (infile) { fclose(infile); } if (outfile) { fclose(outfile); } if (meta) { free(meta); } } int main (int argc, char const *argv[]) { char infile[] = "file.wav"; float factor = 0.5; scale_wav_file(infile, factor, 0); return 0; } I'm getting differing file sizes at the end (by 1k or so, for a 40Mb file), and I suspect this is due to the fact that I'm writing an entire buffer to the output, even though the file may have terminated before filling the entire buffer size. Also, the output file is messed up - won't play or open - so I'm probably doing the whole thing wrong. Any tips on where I'm messing up will be great. Thanks!

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  • Code only runs properly if debugging step-by-step

    - by Cornwell
    Hello, I'm making a webserver and I've come up with some very strange problems. My server was running as expected yesterday when I turned off my laptop, but today it only sends the http headers (I didn't change anything) When a user requests a file, if I send them using the following code, it works perfectly: while ((n = fread(data, 1, sizeof(data), file)) > 0) send(ts, data, n, 0); but if I change it to this, it only sends ~2% of the file. And that's not a random number, it actually only sends about 2% of the file. while ((n = fread(data, 1, sizeof(data), file)) > 0) web.Send(data); int WEB::Send(string data) { return send(TempSocket, data.c_str(), data.size(), 0); } changing string to char* doesn't solve the problem. I'm using visual studio2010. If I run my code step-by-step, I am able to solve problem #1, everything gets sent. And that is my main problem. I do not understand why it happens. Hopefully someone can explain it to me. Thanks in advance. EDIT: int APIENTRY WinMain( HINSTANCE hInstance, HINSTANCE hPrev, LPSTR lpCmd,int nShow) { SOCKET MainSocket=0; MSG msg; RedirectIOToConsole(); CreateThread(NULL, NULL, ListenThread, NULL, NULL, NULL); while (GetMessage(&msg, NULL, 0, 0)) { TranslateMessage(&msg); DispatchMessage(&msg); } WSACleanup(); closesocket(MainSocket); MainSocket = INVALID_SOCKET; return msg.wParam; } DWORD WINAPI ListenThread(LPVOID lparam) { SOCKET MainSocket; WSADATA wsaData; SOCKET tmpsock; struct sockaddr_in local, from; int fromlen=sizeof(from); WSAStartup(MAKEWORD(2, 2), &wsaData); local.sin_family=AF_INET; local.sin_addr.s_addr=INADDR_ANY; local.sin_port=htons(PORT); MainSocket=socket(AF_INET,SOCK_STREAM,0); if(MainSocket==INVALID_SOCKET) { return 0; } if(bind(MainSocket,(struct sockaddr*)&local,sizeof(local))!=0) { return 0; } if(listen(MainSocket,10)!=0) { return 0; } while(1) { tmpsock = accept(MainSocket,(struct sockaddr*)&from,&fromlen); CreateThread(NULL, NULL, SlaveThread, (LPVOID)tmpsock, NULL, NULL); } } DWORD WINAPI SlaveThread(LPVOID lparam) { SOCKET ts = (SOCKET)lparam;//temporary socket ...... char data[4096]; int n; unsigned long int length = statbuf.st_size; web.SendHeaders(200, "OK", format("Content-Disposition: attachment; filename=\"%s\"", FileName.c_str()).c_str(), web.GetMimeType(ReqPath.c_str()), length, statbuf.st_mtime); unsigned long int i=0,d=0; while ((n = fread(data, 1, sizeof(data), file)) > 0) { d+=send(ts, data, n, 0); i+=n; } printf("%i=%i=%i\n", length,i,d); fclose(file);

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  • Segmentation fault on the server, but not local machine

    - by menachem-almog
    As stated in the title, the program is working on my local machine (ubuntu 9.10) but not on the server (linux). It's a grid hosting hosting package of godaddy. Please help.. Here is the code: #include <stdio.h> #include <stdlib.h> int main(int argc, char **argv) { long offset; FILE *io; unsigned char found; unsigned long loc; if (argc != 2) { printf("syntax: find 0000000\n"); return 255; } offset = atol(argv[1]) * (sizeof(unsigned char)+sizeof(unsigned long)); io = fopen("index.dat","rb"); fseek(io,offset,SEEK_SET); fread(&found,sizeof(unsigned char),1,io); fread(&loc,sizeof(unsigned long),1,io); if (found == 1) printf("%d\n",loc); else printf("-1\n"); fclose(io); return 0; } EDIT: It's not my program. I wish I knew enough C in order to fix it, but I'm on a deadline. This program is meant to find the first occurrence of a 7 digit number in the PI sequence, index.dat contains an huge array number = position. http://jclement.ca/fun/pi/search.cgi

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  • Segmentation Fault (C) occur on the server, but works on local machine

    - by menachem-almog
    As stated in the title, the program is working on my local machine (ubuntu 9.10) but not on the server (linux). It's a grid hosting hosting package of godaddy. Please help.. Here is the code: #include <stdio.h> #include <stdlib.h> int main(int argc, char **argv) { long offset; FILE *io; unsigned char found; unsigned long loc; if (argc != 2) { printf("syntax: find 0000000\n"); return 255; } offset = atol(argv[1]) * (sizeof(unsigned char)+sizeof(unsigned long)); io = fopen("index.dat","rb"); fseek(io,offset,SEEK_SET); fread(&found,sizeof(unsigned char),1,io); fread(&loc,sizeof(unsigned long),1,io); if (found == 1) printf("%d\n",loc); else printf("-1\n"); fclose(io); return 0; }

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  • valgrind complains doing a very simple strtok in c

    - by monkeyking
    Hi I'm trying to tokenize a string by loading an entire file into a char[] using fread. For some strange reason it is not always working, and valgrind complains in this very small sample program. Given an input like test.txt first second And the following program #include <stdio.h> #include <string.h> #include <stdlib.h> #include <sys/stat.h> //returns the filesize in bytes size_t fsize(const char* fname){ struct stat st ; stat(fname,&st); return st.st_size; } int main(int argc, char *argv[]){ FILE *fp = NULL; if(NULL==(fp=fopen(argv[1],"r"))){ fprintf(stderr,"\t-> Error reading file:%s\n",argv[1]); return 0; } char buffer[fsize(argv[1])]; fread(buffer,sizeof(char),fsize(argv[1]),fp); char *str = strtok(buffer," \t\n"); while(NULL!=str){ fprintf(stderr,"token is:%s with strlen:%lu\n",str,strlen(str)); str = strtok(NULL," \t\n"); } return 0; } compiling like gcc test.c -std=c99 -ggdb running like ./a.out test.txt thanks

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  • advanced Visual Studio kung-fu test -- Calling functions from the Immediate Window during debugging

    - by kizzx2
    I see some related questions have been asked, but they're either too advanced for me to grasp or lacking a step-by-step guide from start to finish (most of them end up being insider talk of their own experiment results). OK here it is, given this simple program: #include <stdio.h> #include <string.h> int main() { FILE * f; char buffer[100]; memset(buffer, 0, 100); fun(); f = fopen("main.cpp", "r"); fread(buffer, 1, 99, f); printf(buffer); fclose(f); return 0; } What it does is basically print itself (assume file name is main.cpp). Question How can I have it print another file, say foobar.txt without modifying the source code? It has something to do with running it through VS's, stepping through the functions and hijacking the FILE pointer right before fread() is called. No need to worry about leaking resources by calling fclose(). I tried the simple f = fopen("foobar.txt", "r") which gave CXX0017: Error: symbol "fopen" not found Any ideas? Edit I found out the solution accidentally on Debugging Mozilla on Windows FAQ. The correct command to put into the Immediate Window is f = {,,MSVCR100D}fopen("foo.txt", "r") However, it doesn't really answer this question: I still don't understand what is going on here. How to systematically find out the {,,MSVCR100D} part for any given method? I know the MSVCR version changes from system to system. How can I find that out? Could anyone explain the curly brace syntax, especially, what are those two commas doing there? Are there more hidden gems using this syntax?

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  • Calling functions from the Immediate Window during debugging -- advanced Visual Studio kung-fu test

    - by kizzx2
    I see some related questions have been asked, but they're either too advanced for me to grasp or lacking a step-by-step guide from start to finish (most of them end up being insider talk of their own experiment results). OK here it is, given this simple program: #include <stdio.h> #include <string.h> int main() { FILE * f; char buffer[100]; memset(buffer, 0, 100); fun(); f = fopen("main.cpp", "r"); fread(buffer, 1, 99, f); printf(buffer); fclose(f); return 0; } What it does is basically print itself (assume file name is main.cpp). Question How can I have it print another file, say foobar.txt without modifying the source code? It has something to do with running it through VS's, stepping through the functions and hijacking the FILE pointer right before fread() is called. No need to worry about leaking resources by calling fclose(). I tried the simple f = fopen("foobar.txt", "r") which gave CXX0017: Error: symbol "fopen" not found Any ideas?

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  • uploading image & getting back from database

    - by Anup Prakash
    Putting a set of code which is pushing image to database and fetching back from database: <!-- <?php error_reporting(0); // Connect to database $errmsg = ""; if (! @mysql_connect("localhost","root","")) { $errmsg = "Cannot connect to database"; } @mysql_select_db("test"); $q = <<<CREATE create table image ( pid int primary key not null auto_increment, title text, imgdata longblob, friend text) CREATE; @mysql_query($q); // Insert any new image into database if (isset($_POST['submit'])) { move_uploaded_file($_FILES['imagefile']['tmp_name'],"latest.img"); $instr = fopen("latest.img","rb"); $image = addslashes(fread($instr,filesize("latest.img"))); if (strlen($instr) < 149000) { $image_query="insert into image (title, imgdata,friend) values (\"". $_REQUEST['title']. "\", \"". $image. "\",'".$_REQUEST['friend']."')"; mysql_query ($image_query) or die("query error"); } else { $errmsg = "Too large!"; } $resultbytes=''; // Find out about latest image $query = "select * from image where pid=1"; $result = @mysql_query("$query"); $resultrow = @mysql_fetch_assoc($result); $gotten = @mysql_query("select * from image order by pid desc limit 1"); if ($row = @mysql_fetch_assoc($gotten)) { $title = htmlspecialchars($row[title]); $bytes = $row[imgdata]; $resultbytes = $row[imgdata]; $friend=$row[friend]; } else { $errmsg = "There is no image in the database yet"; $title = "no database image available"; // Put up a picture of our training centre $instr = fopen("../wellimg/ctco.jpg","rb"); $bytes = fread($instr,filesize("../wellimg/ctco.jpg")); } if ($resultbytes!='') { echo $resultbytes; } } ?> <html> <head> <title>Upload an image to a database</title> </head> <body bgcolor="#FFFF66"> <form enctype="multipart/form-data" name="file_upload" method="post"> <center> <div id="image" align="center"> <h2>Heres the latest picture</h2> <font color=red><?php echo $errmsg; ?></font> <b><?php echo $title ?></center> </div> <hr> <h2>Please upload a new picture and title</h2> <table align="center"> <tr> <td>Select image to upload: </td> <td><input type="file" name="imagefile"></td> </tr> <tr> <td>Enter the title for picture: </td> <td><input type="text" name="title"></td> </tr> <tr> <td>Enter your friend's name:</td> <td><input type="text" name="friend"></td> </tr> <tr> <td><input type="submit" name="submit" value="submit"></td> <td></td> </tr> </table> </form> </body> </html> --> Above set of code has one problem. The problem is whenever i pressing the "submit" button. It is just displaying the image on a page. But it is leaving all the html codes. even any new line message after the // Printing image on browser echo $resultbytes; //************************// So, for this i put this set of code in html tag: This is other sample code: <!-- <?php error_reporting(0); // Connect to database $errmsg = ""; if (! @mysql_connect("localhost","root","")) { $errmsg = "Cannot connect to database"; } @mysql_select_db("test"); $q = <<<CREATE create table image ( pid int primary key not null auto_increment, title text, imgdata longblob, friend text) CREATE; @mysql_query($q); // Insert any new image into database if (isset($_POST['submit'])) { move_uploaded_file($_FILES['imagefile']['tmp_name'],"latest.img"); $instr = fopen("latest.img","rb"); $image = addslashes(fread($instr,filesize("latest.img"))); if (strlen($instr) < 149000) { $image_query="insert into image (title, imgdata,friend) values (\"". $_REQUEST['title']. "\", \"". $image. "\",'".$_REQUEST['friend']."')"; mysql_query ($image_query) or die("query error"); } else { $errmsg = "Too large!"; } $resultbytes=''; // Find out about latest image $query = "select * from image where pid=1"; $result = @mysql_query("$query"); $resultrow = @mysql_fetch_assoc($result); $gotten = @mysql_query("select * from image order by pid desc limit 1"); if ($row = @mysql_fetch_assoc($gotten)) { $title = htmlspecialchars($row[title]); $bytes = $row[imgdata]; $resultbytes = $row[imgdata]; $friend=$row[friend]; } else { $errmsg = "There is no image in the database yet"; $title = "no database image available"; // Put up a picture of our training centre $instr = fopen("../wellimg/ctco.jpg","rb"); $bytes = fread($instr,filesize("../wellimg/ctco.jpg")); } } ?> <html> <head> <title>Upload an image to a database</title> </head> <body bgcolor="#FFFF66"> <form enctype="multipart/form-data" name="file_upload" method="post"> <center> <div id="image" align="center"> <h2>Heres the latest picture</h2> <?php if ($resultbytes!='') { // Printing image on browser echo $resultbytes; } ?> <font color=red><?php echo $errmsg; ?></font> <b><?php echo $title ?></center> </div> <hr> <h2>Please upload a new picture and title</h2> <table align="center"> <tr> <td>Select image to upload: </td> <td><input type="file" name="imagefile"></td> </tr> <tr> <td>Enter the title for picture: </td> <td><input type="text" name="title"></td> </tr> <tr> <td>Enter your friend's name:</td> <td><input type="text" name="friend"></td> </tr> <tr> <td><input type="submit" name="submit" value="submit"></td> <td></td> </tr> </table> </form> </body> </html> --> ** But in this It is showing the image in format of special charaters and digits. 1) So, Please help me to print the image with some HTML code. So that i can print it in my form to display the image. 2) Is there any way to convert the database image into real image, so that i can store it into my hard-disk and call it from tag? Please help me.

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  • Getting zeros between data while reading a binary file in C

    - by indiajoe
    I have a binary data which I am reading into an array of long integers using a C programme. hexdump of the binary data shows, that after first few data points , it starts again at a location 20000 hexa adresses away. hexdump output is as shown below. 0000000 0000 0000 0000 0000 0000 0000 0000 0000 * 0020000 0000 0000 0053 0000 0064 0000 006b 0000 0020010 0066 0000 0068 0000 0066 0000 005d 0000 0020020 0087 0000 0059 0000 0062 0000 0066 0000 ........ and so on... But when I read it into an array 'data' of long integers. by the typical fread command fread(data,sizeof(*data),filelength/sizeof(*data),fd); It is filling up with all zeros in my data array till it reaches the 20000 location. After that it reads in data correctly. Why is it reading regions where my file is not there? Or how will I make it read only my file, not anything inbetween which are not in file? I know it looks like a trivial problem, but I cannot figure it out even after googling one night.. Can anyone suggest me where I am doing it wrong? Other Info : I am working on a gnu/linux machine. (slax-atma distro to be specific) My C compiler is gcc.

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