system(3) Library Functions Manual system(3)
NAME
system - Executes a shell command
LIBRARY
Standard C Library (libc.so, libc.a)
SYNOPSIS
#include <stdlib.h>
int system(
const char *string);
STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:
system(): XPG4, XPG4-UNIX
Refer to the standards(5) reference page for more information about industry standards and associated tags.
PARAMETERS
Specifies 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 exe-
cutes 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.
RETURN VALUES
If the string parameter is NULL, the system() function returns 0 if it is unable to access the command interpreter or a non-zero 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
The system() function sets errno to the specified values for the following conditions: The status of the child process created by system()
is no longer available.
In addition, the system() function may set errno values as described by fork().
RELATED INFORMATION
Functions: exec(2), exit(2), fork(2), wait(2)
Commands: sh(1)
Standards: standards(5) delim off
system(3)