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NAME

system - execute a shell command

SYNOPSIS

#include <stdlib.h>
int system (const char * string);

DESCRIPTION

system() executes a command specified in string by calling /bin/sh -c string, and returns after the command has been completed. During execution of the command, SIGCHLD will be blocked, and SIGINT and SIGQUIT will be ignored.

RETURN VALUE

The value returned is 127 if the execve() call for /bin/sh fails, -1 if there was another error and the return code of the command otherwise.

If the value of string is NULL, system() returns nonzero if the shell is available, and zero if not.

system() does not affect the wait status of any other children.

CONFORMS TO

ANSI C, POSIX.1, proposed POSIX.2, BSD 4.3

BUGS

Do not use system() from a program with suid or sgid privileges, because strange values for some environment variables might be used to subvert system integrity. Use the exec(2) family of functions instead, but not execlp(2) or execvp(2).

The check for the availability of /bin/sh is not actually performed; it is always assumed to be available.

It is possible for the shell command to return 127, so that code is not a sure indication that the execve() call failed; check errno to make sure.

SEE ALSO

sh(1), exec(2), signal(2)

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