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Top Forums UNIX for Dummies Questions & Answers How to write to stdin of another program (program A -> [stdin]program B) Post 302220960 by jim mcnamara on Saturday 2nd of August 2008 12:40:35 PM
Old 08-02-2008
Also note: popen is a one way deal - you choose either to write to or to read from a child process, popen will not let you do both at the same time. Otherwise, you get into more interesting and advanced interprocess communication (IPC) programming like maybe pipes.
 

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pclose(3)						     Library Functions Manual							 pclose(3)

NAME
pclose - Closes a pipe to a process LIBRARY
Standard C Library (libc.so, libc.a) SYNOPSIS
#include <stdio.h> int pclose ( FILE *stream ); STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: pclose(): XPG4, XPG4-UNIX Refer to the standards(5) reference page for more information about industry standards and associated tags. PARAMETERS
Points to a FILE structure for an open pipe returned by a previous call to the popen() function. DESCRIPTION
The pclose() function closes a pipe between the calling program and a shell command to be executed. Use the pclose() function to close any stream you have opened with the popen() function. The pclose() function waits for the associated process to end, and then returns the exit status of the command. If the original processes and the process started with the popen() function concurrently read or write a common file, neither should use buffered I/O. If they do, the results are unpredictable. RETURN VALUES
Upon successful completion, the pclose() function returns the exit status of the command. If an error is detected, pclose() sets errno to an appropriate value and returns a value of -1. ERRORS
If the pclose() function fails, errno may be set to the following value: The status of the child process could not be obtained. RELATED INFORMATION
Functions: fclose(3), popen(3), wait(2) Standards: standards(5) delim off pclose(3)
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