ultrix man page for popen

popen(3)						     Library Functions Manual							  popen(3)

Name
       popen, pclose - initiate I/O to/from a process

Syntax
       #include <stdio.h>

       FILE *popen(command, type)
       char *command, *type;

       pclose(stream)
       FILE *stream;

Description
       The arguments to are pointers to null-terminated strings containing respectively a shell command line and an I/O mode, either "r" for read-
       ing or "w" for writing.	It creates a pipe between the calling process and the command to be executed.  The  value  returned  is  a  stream
       pointer that can be used (as appropriate) to write to the standard input of the command or read from its standard output.

       A stream opened by should be closed by which waits for the associated process to terminate and returns the exit status of the command.

       Because open files are shared, a type "r" command may be used as an input filter, and a type "w" as an output filter.

Diagnostics
       The routine returns a null pointer if files or processes cannot be created, or the shell cannot be accessed.

       The routine returns -1 if stream is not associated with a `popened' command.

Restrictions
       Buffered reading before opening an input filter may leave the standard input of that filter mispositioned.  Similar problems with an output
       filter may be forestalled by careful buffer flushing, for instance, with For further information, see

       The routine always calls and never calls

See Also
       sh(1), pipe(2), wait(2), system(3), fclose(3s), fopen(3s)

																	  popen(3)