system_safe, system_execs, system_nosh - execute a command with its arguments from a string without using

       Renzo Davoli <renzo@cs.unibo.it>

VirtualSquare                                      2014-05-27                                     system_safe(3)

       Bug reports should be addressed to <info@virtualsquare.org>

system_safe  is  a  safe  replacement  for system(3) provided by the libc. system_safe parses the command
       string and runs the command directly, without using a shell. The command must be specified as an absolute
       pathname. system_safe does not support variables as argument.
       Command arguments in args are delimited by space characters (blank, tabs or new lines).  Single or double
       quotes can be used to delimitate command arguments including spaces and a non quoted backslash (\) is the
       escape character to protect the next char.
       system_execsa is like system_safe supporting also variables as arguments.  When an argument of a  command
       is  a  dollar sign followed by a name (e.g. $USER) s2argv puts the output of  the  s2argv_getvar function
       instead. (It is possible for example to assign s2argv_getvar=getenv.  For security reasons, the  function
       is  NULL  by  default and all variables get replaced with an empty string.  Programmers can use their own
       custom function instead)
       In system_execsp the executable file is sought using the  PATH  environment  variable  as  explained  for
       execlp(3).
       system_execs  requires  the  path of the executable to be specified as its first parameter so it does not
       use the PATH environment variable.
       system_execsr, system_execsrp and system_execsra works as their couterparts without  the  'r',  but  they
       permit  the redirection of standard input, output and error streams.  Their last parameter is an array of
       three integers.  The standard input of the command will be redirected to redir[0] if it is positive,  the
       standard output to redir[1] if it is not negative and different from 1, the standard error to redir[2] if
       it is not negative and different from 2.
       system_execsra does not use the PATH variable, argv[0] must be specified as a full pathname.
       system_nosh,  system_execsqp,  system_execsqa,  system_execsqrp  and system_execsqra can run sequences of
       commands separated by semicolons (;).  The first command returning a  non-zero  exit  status  breaks  the
       sequence.
       system_nosh  is  an  almost  drop in replacement for system(3) provided by the libc.  (system_execsqp and
       system_nosh are synonyms).

       The following program shows the usage of system_nosh:

       #include <stdio.h>
       #include <unistd.h>
       #include <execs.h>

       #define BUFLEN 1024
       int main(int argc, char *argv)
       {
            char buf[BUFLEN];
            printf("type in a command and its arguments, e.g. 'ls -l'\n");
            while (fgets(buf, BUFLEN, stdin) != NULL) {
                 printf("Command: '%s' \n",buf);
                 system_nosh(buf);
                 printf("Command done\n");
            }
       }

       system_safe, system_execs, system_nosh - execute a command with its arguments from a string without using
       a shell

       These functions have the same return values of system(3). When running a sequence of commands, it returns
       the "wait status" of the first command returning a non-zero value. If the return value is zero  it  means
       that all the commands of the sequence succeeded.

system(3),execs(3),s2argv(3)

#include<stdlib.h>#include<execs.h>intsystem_safe(constchar*command);intsystem_execsp(constchar*command);intsystem_execsa(constchar*command);intsystem_execs(constchar*path,charconst*command);intsystem_execsrp(constchar*command,intredir[3]);intsystem_execsra(constchar*command,intredir[3]);intsystem_execsr(constchar*path,charconst*command,intredir[3]);intsystem_nosh(constchar*command);intsystem_execsqp(constchar*command);intsystem_execsqa(constchar*command);intsystem_execsqrp(constchar*command,intredir[3]);intsystem_execsqra(constchar*command,intredir[3]);

       These functions are provided by libexecs. Link with -lexecs.