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system(3c) [opensolaris man page]

system(3C)						   Standard C Library Functions 						system(3C)

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). The system() function sets the SIGINT and SIGQUIT signals to be ignored, and blocks the SIGCHLD signal for the calling thread, while wait- ing for the command to terminate. The system() function does not affect the termination status of any child of the calling processes other than the process it creates. The termination status of the process created by the system() function is not affected by the actions of other threads in the calling process (it is invisible to wait(3C)) or by the disposition of the SIGCHLD signal in the calling process, even if it is set to be ignored. No SIGCHLD signal is sent to the process containing the calling thread when the command terminates. RETURN VALUES
The system() function executes posix_spawn(3C) to create a child process running the shell that in turn executes the commands in string. If posix_spawn() fails, system() returns -1 and sets errno to indicate the error; otherwise the exit status of the shell is returned. ERRORS
The system() function may set errno values as described by fork(2), in particular: EAGAIN A resource control or limit on the total number of processes, tasks or LWPs under execution by a single user, task, project, or zone has been exceeded, or the total amount of system memory available is temporarily insufficient to duplicate this process. ENOMEM There is not enough swap space. EPERM The {PRIV_PROC_FORK} privilege is not asserted in the effective set of the calling process. USAGE
The system() function manipulates the signal handlers for SIGINT and SIGQUIT. 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), popen(3C), posix_spawn(3C), wait(3C), waitpid(3C), attributes(5), standards(5) SunOS 5.11 14 Dec 2006 system(3C)

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waitpid(3C)                                                Standard C Library Functions                                                waitpid(3C)

NAME
waitpid - wait for child process to change state SYNOPSIS
#include <sys/types.h> #include <sys/wait.h> pid_t waitpid(pid_t pid, int *stat_loc, int options); DESCRIPTION
The waitpid() function will suspend execution of the calling thread until status information for one of its terminated child processes is available, or until delivery of a signal whose action is either to execute a signal-catching function or to terminate the process. If more than one thread is suspended in waitpid(), wait(3C), or waitid(2) awaiting termination of the same process, exactly one thread will return the process status at the time of the target process termination. If status information is available prior to the call to waitpid(), return will be immediate. The pid argument specifies a set of child processes for which status is requested, as follows: o If pid is equal to (pid_t)-1, status is requested for any child process. If pid is greater than (pid_t)0, it specifies the process ID of the child process for which status is requested. o If pid is equal to (pid_t)0 status is requested for any child process whose process group ID is equal to that of the calling process. o If pid is less than (pid_t)-1, status is requested for any child process whose process group ID is equal to the absolute value of pid. One instance of a SIGCHLD signal is queued for each child process whose status has changed. If waitpid() returns because the status of a child process is available, and WNOWAIT was not specified in options, any pending SIGCHLD signal associated with the process ID of that child process is discarded. Any other pending SIGCHLD signals remain pending. If the calling process has SA_NOCLDWAIT set or has SIGCHLD set to SIG_IGN and the process has no unwaited children that were transformed into zombie processes, it will block until all of its children terminate, and waitpid() will fail and set errno to ECHILD. If waitpid() returns because the status of a child process is available, then that status may be evaluated with the macros defined by wait.h(3HEAD) If the calling process had specified a non-zero value of stat_loc, the status of the child process will be stored in the location pointed to by stat_loc. The options argument is constructed from the bitwise-inclusive OR of zero or more of the following flags, defined in the header <sys/wait.h>: WCONTINUED The status of any continued child process specified by pid, whose status has not been reported since it continued, is also reported to the calling process. WNOHANG The waitpid() function will not suspend execution of the calling process if status is not immediately available for one of the child processes specified by pid. WNOWAIT Keep the process whose status is returned in stat_loc in a waitable state. The process may be waited for again with identi- cal results. WUNTRACED The status of any child processes specified by pid that are stopped, and whose status has not yet been reported since they stopped, is also reported to the calling process. WSTOPPED is a synonym for WUNTRACED. RETURN VALUES
If waitpid() returns because the status of a child process is available, it returns a value equal to the process ID of the child process for which status is reported. If waitpid() returns due to the delivery of a signal to the calling process, -1 is returned and errno is set to EINTR. If waitpid() was invoked with WNOHANG set in options, it has at least one child process specified by pid for which status is not available, and status is not available for any process specified by pid, then 0 is returned. Otherwise, -1 is returned and errno is set to indicate the error. ERRORS
The waitpid() function will fail if: ECHILD The process or process group specified by pid does not exist or is not a child of the calling process or can never be in the states specified by options. EINTR The waitpid() function was interrupted due to the receipt of a signal sent by the calling process. EINVAL An invalid value was specified for options. USAGE
With options equal to 0 and pid equal to (pid_t)-1, waitpid() is identical to wait(3C). The waitpid() function is implemented as a call to the more general waitid(2) function. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |Async-Signal-Safe | +-----------------------------+-----------------------------+ SEE ALSO
intro(2), exec(2), exit(2), fork(2), pause(2), sigaction(2), ptrace(3C), signal(3C), siginfo.h(3HEAD), wait(3C), waitpid(3C), wait.h(3HEAD), attributes(5), standards(5) SunOS 5.10 19 Jun 2003 waitpid(3C)

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