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)
