System Calls

Alarm(s) : RngIntElt ->

A procedure which when used on UNIX systems, sends the signal SIGALRM to the Magma process after s seconds. This allows the user to specify that a Magma-process should self-destruct after a certain period.

ChangeDirectory(s) : MonStgElt ->

Change to the directory specified by the string s. Tilde expansion is allowed.

GetCurrentDirectory() : ->

Returns the current directory as a string.

Getpid() : ->

Returns Magma's process ID (value of the Unix C system call getpid()).

Getuid() : ->

Returns the user ID (value of the Unix C system call getuid()).

Fork() : -> RngIntElt

    ExitSummary: BoolElt                Default: false

Execute the Unix/Linux system call fork() and return the process ID of the child (if now the parent), or return 0 (if now the child). If the parameter ExitSummary is set to true, then the child process prints the usual exit summary ("Total time: ...") when it exits; otherwise this is suppressed (the default).

System(C) : MonStgElt -> RngIntElt

Execute the system command specified by the string C. This is done by calling the C function system().

This also returns the system command's return value as an integer. On most Unix systems, the lower 8 bits of this value give the process status while the next 8 bits give the value given by the command to the C function exit() (see the Unix manual entries for system(3) or wait(2), for example). Thus one should normally divide the result by 256 to get the exit value of the program on success.

See also the Pipe intrinsic function.

> System("date");
Tue Feb 28 13:02:03 EST 2017