C system() how to send the output to an array?? Post: 302388288

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Top Forums Programming C system() how to send the output to an array?? Post 302388288 by pludi on Wednesday 20th of January 2010 02:17:36 AM

01-20-2010

Registered User

From the man page of strcat (emphasis added)

Quote:

The strcat() function appends the src string to the dest string, overwriting the null byte ('\0') at the end of dest, and then adds a terminating null byte. The strings may not overlap, and the dest string must have enough space for the result.[...]
If src contains n or more characters, strcat() writes n+1 characters to dest (n from src plus the terminating null byte). Therefore, the size of dest must be at least strlen(dest)+n+1.

So as soon as you read more that 512 bytes from the process (which, with netstat will happen almost guaranteed) you'll start trying to write into unreserved space. This space might already be claimed by another process, and so the system intervenes.

One approach might be to allocate a large enough part of memory at the beginning.
A better approach would be to allocate a bit of memory using malloc(), and expanding that if needed using realloc().

pludi

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LEARN ABOUT DEBIAN

ascommand

ASCOMMAND(1x)															     ASCOMMAND(1x)

NAME

       ascommand - send commands to AfterStep

SYNOPSIS

       ascommand [-f file] [-h] [-i] [-v] [-w id] [--] [command]

DESCRIPTION

       This  manual  page  documents briefly the ascommand command.  This manual page was written for the Debian distribution because the original
       program does not have a manual page.

       ascommand is a program, which sends commands to the AfterStep Window Manager.

OPTIONS

       -f --file
	      input commands from file (- means stdin)

       -h --help
	      this help

       -i --interactive starts interactive communication with AfterStep

       -v --version
	      print version information

       -w --window-id
	      window id to send to AfterStep (in hex)

       --     end parsing of command line options

       command
	      command to send to AfterStep

       If -f - or -i is specified, ascommand will read commands from standard input, and print results on standard output.  -i is noisier than	-f
       -.

SEE ALSO

       afterstep(1x).

AUTHOR

       This  manual page was written by Robert Luberda <robert@debian.org>, using help2man(1) program, for the Debian GNU/Linux system (but may be
       used by others).

								  May 28th, 2006						     ASCOMMAND(1x)

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