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system(3C)

Name | Synopsis | Description | Return Values | Errors | Usage | Attributes | See Also

Name

system– issue a shell command

Synopsis

#include <stdlib.h>

int system(const char *string);

Description

The system() function causes string to be given to the shell as input, as if string had been typed as a command at a terminal. The invoker waits until the shell has completed, then returns the exit status of the shell in the format specified by waitpid(3C).

If string is a null pointer, system() checks if the shell exists and is executable. If the shell is available, system() returns a non-zero value; otherwise, it returns 0. The standard to which the caller conforms determines which shell is used. See standards(5).

Return Values

The system() function executes vfork(2) to create a child process that in turn invokes one of the exec family of functions (see exec(2)) on the shell to execute string. If vfork() or the exec function fails, system() returns -1 and sets errno to indicate the error.

Errors

The system() function fails if:

EAGAIN

The system-imposed limit on the total number of processes under execution by a single user would be exceeded.

EINTR

The system() function was interrupted by a signal.

ENOMEM

The new process requires more memory than is available.

Usage

The system() function manipulates the signal handlers for SIGINT, SIGQUIT, and SIGCHLD. It is therefore not safe to call system() in a multithreaded process, since some other thread that manipulates these signal handlers and a thread that concurrently calls system() can interfere with each other in a destructive manner. If, however, no such other thread is active, system() can safely be called concurrently from multiple threads. See popen(3C) for an alternative to system() that is thread-safe.

Attributes

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Interface Stability	Standard
MT-Level	Unsafe

See Also

ksh(1), sh(1), exec(2), vfork(2), popen(3C), waitpid(3C), attributes(5), standards(5)

Name | Synopsis | Description | Return Values | Errors | Usage | Attributes | See Also