NAME

system −  Executes a shell command

LIBRARY

Standard C Library (libc.a)

SYNOPSIS

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

PARAMETERS

stringSpecifies a valid sh shell command. 

If string is NULL (0), the system() function tests the accessibility of the sh command interpreter. 

If string is not NULL, the system() function passes the parameter to the sh command, which interprets string as a command and executes it. 

DESCRIPTION

The system() function passes the string parameter to the sh command, which interprets string as a command and executes it. 

The system() function invokes the fork() function to create a child process that in turn uses the exec function to run sh, which interprets the shell command contained in the string parameter.  The current process waits until the shell has completed before returning. 

NOTES

AES Support Level:
Full use

RETURN VALUES

If the string parameter is NULL, the system() function returns 0 if it is unable to access the command interpreter or a positive value if sh is accessible. 

If the string parameter is not NULL, upon successful completion by sh, the system() function returns the exit status of the shell process in the form that wait(2) returns.  Otherwise, the system() function returns a value of −1 and sets errno to indicate the error. 

Exit status 127 indicates that the shell could not be executed. 

Note that the exit status should only be interpreted using the macros described in wait(2) and defined in the sys/wait.h header file. 

ERRORS

If the system() function fails, errno may be set to one of the following values:

[EAGAIN]The system-imposed limit on the total number of processes under execution, system-wide or by a single user ID, would be exceeded. 

[EINTR]The system() function was interrupted by a signal which was caught. 

[ENOMEM]There is not enough space left for this process. 

RELATED INFORMATION

Functions: exec(2), exit(2), fork(2), wait(2)

Commands: sh(1)