1.4.50 system: Execute a System Command

The function is called by:

Example: system():

       character*8 string / ’ls s*’ /
       INTEGER*4 status, system
       status = system( string )
       if ( status .ne. 0 ) stop ’system: error’
       end

The function system passes string to your shell as input, as if the string had been typed as a command. Note: string cannot be longer than 1024 characters.

If system can find the environment variable SHELL, then system uses the value of SHELL as the command interpreter (shell); otherwise, it uses sh(1).

The current process waits until the command terminates.

Historically, cc developed with different assumptions:

• If cc calls system, the shell is always the Bourne shell.

The system function flushes all open files:

• For output files, the buffer is flushed to the actual file.

• For input files, the position of the pointer is unpredictable.

The functions sh(3f) and system(3f) pass the argument string to a shell for execution. They convert the argument string from a Fortran character value to a C string value and pass it to the C routine system(3c). The routines sh(3f) and system(3f) differ in that system flushes the Fortran I/O buffers before calling the C routine system, while sh does not. Flushing the buffers can take significant time, and so, if any Fortran output is irrelevant to the result of the call, the routine sh is preferred over the routine system.

See also: execve(2), wait(2), and system(3).

The system() function is not MT-safe. Do not call it from multithreaded or parallelized programs.