input/output redirection

(operating system)In Unix, to send ouput from a processto different file or device or to another process via apipe, or to have a process read its input from a differentfile, device or pipe. Some other operating systems havesimilar 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 theinput of another

who | wc -l

A common misuse by beginners is

cat myfile | myprog

Which is more or less equivalent to "myprog < myfile" exceptthat it introduces an extra unnecessary cat process and bufferspace for the pipe. Even the "
Unix's concept of standard input/output and I/O redirectionmake it easy to combine simple processes in powerful ways andto use the same commands for different purposes.

单词	input/output redirection
释义	input/output redirection input/output redirection (operating system)In Unix, to send ouput from a processto different file or device or to another process via apipe, or to have a process read its input from a differentfile, device or pipe. Some other operating systems havesimilar 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 theinput of another who \| wc -l A common misuse by beginners is cat myfile \| myprog Which is more or less equivalent to "myprog < myfile" exceptthat it introduces an extra unnecessary cat process and bufferspace for the pipe. Even the " Unix's concept of standard input/output and I/O redirectionmake it easy to combine simple processes in powerful ways andto use the same commands for different purposes.
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