Home Articles FAQs XREF Games Software Instant Books BBS About FOLDOC RFCs Feedback Sitemap

input/output redirection

You are here: irt.org | FOLDOC | input%2foutput redirection

<operating system> In Unix, to send ouput from a process to different file or device or to another process via a pipe, or to have a process read its input from a different file, device or pipe. Some other operating systems have similar facilities.

To redirect input to come from a file instead of the keyboard, use "<":

	myprog < myfile

Similarly to redirect output to a file instead of the screen:

	ls > filelist

A pipe redirects the output of one process directly into the input of another

	who | wc -l

A common misuse by beginners is

	cat myfile | myprog

Which is more or less equivalent to "myprog < myfile" except that it introduces an extra unnecessary cat process and buffer space for the pipe. Even the "<" is unnecessary with many standard Unix commands since they accept input file names as command line arguments anyway.

Unix's concept of standard input/output and I/O redirection make it easy to combine simple processes in powerful ways and to use the same commands for different purposes.


Nearby terms: input « input device « input/output « input/output redirection » inquiry/response system » INRIA » insanely great

FOLDOC, Topics, A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, ?, ALL

©2018 Martin Webb