Ubuntu Manpage: system_nosh, system_execs - execute a command with its arguments from a string without using a shell

NAME

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

SYNOPSIS

       #include <stdlib.h>
       #include <execs.h>

       int system_nosh(const char *command);
       int system_execsp(const char *command);

       int system_execsa(const char *command);
       int system_execs(const char *path, char const *command);

       int system_execsrp(const char *command, int redir[3]);

       int system_execsra(const char *command, int redir[3]);
       int system_execsr(const char *path, char const *command, int redir[3]);

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

DESCRIPTION

system_nosh is an almost drop in replacement for system(3) provided by the libc. system_nosh parses the
command string and runs the command directly, without using a shell. (system_execsp and system_nosh are
synonyms).
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. 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_execsa does not use the PATH variable, argv[0] must be specified as a full pathname.
system_execsrp and system_execsr 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.
All these functions can run sequences of commands separated by semicolons (;). The first command
returning a non-zero exit status breaks the sequence.

RETURN VALUE

       These functions have the same return values of system(3). When running a sequence of commands, it returns
       the  exit  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.

EXAMPLE

       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");
            }
       }

BUGS

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

AUTHOR

       Renzo Davoli <renzo@cs.unibo.it>