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Full Discussion: C system() how to send the output to an array??
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
Old 01-20-2010
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().
 

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LEARN ABOUT CENTOS

fftw-wisdom-to-conf

FFTW-WISDOM-TO-CONF(1)						       fftw						    FFTW-WISDOM-TO-CONF(1)

NAME

       fftw-wisdom-to-conf - generate FFTW wisdom (pre-planned transforms)

SYNOPSIS

       fftw-wisdom-to-conf [< INPUT] [> OUTPUT]

DESCRIPTION

       fftw-wisdom-to-conf  is	a  utility to generate C configuration routines from FFTW wisdom files, where the latter contain saved information
       about how to optimally compute (Fourier) transforms of various sizes.  A configuration routine is a C subroutine that you  link	into  your
       program, replacing a routine of the same name in the FFTW library, that determines which parts of FFTW are callable by your program.

       The reason to do this is that, if you only need transforms of a limited set of sizes and types, and if you are statically linking your pro-
       gram, then using a configuration file generated from wisdom for those types can substantially reduce the size of your executable.   (Other-
       wise, because of FFTW's dynamic nature, all of FFTW's transform code must be linked into any program using FFTW.)

       FFTW  is a free library to compute discrete Fourier transforms in one or more dimensions, for arbitrary sizes, and of both real and complex
       data, among other related operations.  More information on FFTW can be found at the FFTW home page: http://www.fftw.org

       fftw-wisdom-to-conf reads wisdom from standard input and writes the configuration to standard output.  It can easily be combined  with  the
       fftw-wisdom tool, for example:

       fftw-wisdom -n cof1024 cob1024 -o wisdom
       fftw-wisdom-to-conf < wisdom > conf.c

       will  create  a	configuration "conf.c" containing only those parts of FFTW needed for the optimized complex forwards and backwards out-of-
       place transforms of size 1024 (also saving the wisdom itself in "wisdom").

       Alternatively, you can run your actual program, export wisdom for all plans that were created (ideally in FFTW_PATIENT  or  FFTW_EXHAUSTIVE
       mode), use this as input for fftw-wisdom-to-conf, and then re-link your program with the resulting configuration routine.

       Note  that  the	configuration  routine	does  not contain the wisdom, only the routines necessary to implement the wisdom, so your program
       should also import the wisdom in order to benefit from the pre-optimized plans.

OPTIONS

       -h, --help
	      Display help on the command-line options and usage.

       -V, --version
	      Print the version number and copyright information.

BUGS

       Send bug reports to fftw@fftw.org.

AUTHORS

       Written by Steven G. Johnson and Matteo Frigo.

       Copyright (c) 2003, 2007-11 Matteo Frigo
       Copyright (c) 2003, 2007-11 Massachusetts Institute of Technology

SEE ALSO

       fftw-wisdom(1)

fftw								  February, 2003					    FFTW-WISDOM-TO-CONF(1)
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