input/output 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.
(1998-04-24)
Nearby terms:
input « input device « input/output «
input/output redirection » inquiry/response
system » INRIA » insanely great
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