NAME

kjb_system_2 - A helper for kjb_system(), wrapper for system()

SYNOPSIS

#include "l/l_sys_lib.h"

Example compile flags (system dependent):
  -DLINUX_X86_64 -DLINUX_X86_64_OPTERON  -DGNU_COMPILER 
   -I/home/kobus/include
   -L/home/kobus/misc/load/linux_x86_64_opteron -L/usr/lib/x86_64-linux-gnu
  -lKJB                               -lfftw3  -lgsl -lgslcblas -ljpeg  -lSVM -lstdc++                    -lpthread -lSLATEC -lg2c    -lacml -lacml_mv -lblas -lg2c      -lncursesw 


int kjb_system_2
(
	const char *command,
	int *prog_rc_ptr
);

DESCRIPTION

This function is different than kjb_system() in that 1) it dodges the process that sits in the background to handle incomming system call requests; and 2) it provides a simple return code for the command executed (if argument prog_rc_ptr is not NULL). It is different than system() in that output to stderr is collected as error messages (until the space for them is used up, in which case they should be dropped --- we should check this still work!). If argument prog_rc_ptr is not NULL, then *prog_rc_ptr will be set to the shell return codes by the following table (not everything has been checked), and, if none of these apply, then the return code of what running program chooses to return, as you would expect. | 1 Catchall for general errors

  2     Misuse of shell builtins
  126   Command invoked cannot execute
  127   "command not found"
  128   Invalid argument to exit
  128+n Fatal error signal "n"
  255   Exit status out of range

This function has historical baggage due to trying to do what seems hard to do easily which is to separate out the notions of 1) the shell failing to get the command(s) running with the various IO redirections; and 2) the subsequently well formed command reports an error return code. This is not implemented due to difficulties --- it seems that doing so in the general case would require parsing composite commands into smaller commands, checking that they can be executed, and checking the IO redirects. Currently, the cases we cannot handle well are composite cases that we do not want to do this analysis, and so we adopt the shell's version of the situation, which means that something like:

  ls < NON_EXISTANT

will have an error code of "1" which may or may not be what we want (but it is consistant with the shell). However,

 NON_EXISTANT

will get return code "127", and

 NON_PERMITTED

will get return code "126".

DISCLAIMER

This software is not adequatedly tested. It is recomended that results are checked independantly where appropriate.

AUTHOR

Kobus Barnard

DOCUMENTER