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Top Forums UNIX for Dummies Questions & Answers Write/read to file descriptors Post 302275626 by machshev on Sunday 11th of January 2009 04:19:21 PM
Old 01-11-2009
Thank you for getting back to me. I understand that stdin is normally used for incoming data (from the keyboard) and that we usually write to stdout and/or stderr. I was just wondering how I could write something to stdin and read from stdout and/or stderr. I figure that it involves the file descriptors and using pipes but I'm really not sure how that works.
 

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dup(2)								System Calls Manual							    dup(2)

NAME
dup - duplicate an open file descriptor SYNOPSIS
DESCRIPTION
fildes is a file descriptor obtained from a or system call. returns a new file descriptor having the following in common with the origi- nal: o Same open file (or pipe). o Same file pointer (i.e., both file descriptors share one file pointer). o Same access mode (read, write or read/write). o Same file status flags (see fcntl(2), The new file descriptor is set to remain open across system calls. See fcntl(2). The file descriptor returned is the lowest one available. RETURN VALUE
Upon successful completion, the file descriptor is returned as a non-negative integer. Otherwise, a value of -1 is returned and is set to indicate the error. ERRORS
fails if one or more of the following is true: fildes is not a valid open file descriptor. Request violates the maximum number of open file descriptors. AUTHOR
was developed by AT&T and HP. SEE ALSO
close(2), creat(2), dup2(2), exec(2), fcntl(2), open(2), pipe(2), privileges(5). STANDARDS CONFORMANCE
dup(2)
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