system(3) [osf1 man page]
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)
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times(3) Library Functions Manual times(3) NAME
times - Gets process and child process times LIBRARY
Standard C Library (libc.so, libc.a) SYNOPSIS
#include <sys/times.h> clock_t times( struct tms *buffer); Programs that are being developed for conformance to the AT&T System V Interface Definition must specify two #include statements, as fol- lows: #include <sys/types.h> #include <sys/times.h> STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: times(): XPG4, XPG4-UNIX Refer to the standards(5) reference page for more information about industry standards and associated tags. PARAMETERS
Points to type tms structure space where system time information is stored. DESCRIPTION
The times() function fills the type tms structure space pointed to by the buffer parameter with time-accounting information. All time val- ues reported by this function are in hardware-dependent clock ticks. The times of a terminated child process are included in the tms_cutime and tms_cstime elements of the parent process when a wait function returns the process ID of that terminated child. The tms structure, which is defined in the sys/times.h header file, contains the following members: User time. The CPU time charged while executing user instructions of the calling process. System time. The CPU time charged during system execution on behalf of the calling process. User time, children. The sum of the tms_utime and the tms_cutime times of the child processes. System time, children. The sum of the tms_stime and the tms_cstime times of the child processes. When a child process does not wait for its children, its child-process times are not included in its times. This information comes from the calling process and each of its terminated child processes for which a wait function has been executed. RETURN VALUES
Upon successful completion, the times() function returns the elapsed real time since an arbitrary reference time in the past (for example, system start-up time). The reference time does not change from one invocation of times() within the process to another. The elapsed times are in units of 1/CLK_TCK seconds, where CLK_TCK is processor dependent. For application portability, the value of CLK_TCK should be queried using the sysconf() function (see sysconf(3)). The return value may overflow the possible range of type clock_t values. When the times() function fails, a value of (clock_t)-1 is returned. RELATED INFORMATION
Commands: cc(1) Functions: exec(2), fork(2), getrusage(2), profil(2), stime(3), sysconf(3), time(3), wait(2) Standards: standards(5) delim off times(3)