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Redirection of program output

People often want to record the output of a program in order to process it. It is called "output redirection".

For example, if you want to record the output of the ls command in a "lsbin.txt" file (in your home directory), type:

ls /bin > ~/lsbin.txt
If the lsbin file already exists, its contents will be erased. To avoid this, type >> instead of > (this permits you to append the "ls" stream to the end of the lsbin.txt file)

Generally, the contents of a file or a directory scroll too rapidly on your screen and you do not have enough time to read them. A solution to this consists of saving the output of a command and then using the utility program "more" to read it ("more" is an editor which displays a text page after page).

So, you have to type:

ls /bin > ~/lsbin.txt

more ~/lsbin
Linux proposes a more "elegant" method which consists of using pipes. With this method, the output of one command is sent to the input of another command. The result is:

ls /bin | more
Here, the output of the ls command is sent to "more" to be processed. You can combine different pipes to carry out complex procedures.


next up previous contents
Next: Understanding the processes Up: How to use your Previous: Using Linux multitask system   Contents

1999-01-27