Is it possible to direct your output file having the same name as input file, that is to overwrite?

I would like to overwrite the name of input file with the same name of output file owing to limited disk space that I have in my system. Is it possible? I know this is not recommended, but I have the input files already backup. I will have a loop in a shell to do the cut command.

#!/bin/bash
for i in {1..1000}
do
    cut --delimiter=' ' --fields=1,3-7 input$i.t开发者_如何学Pythonxt > input$i.txt
done

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You could always use a temporary file to which you redirect, and then when you're sure everything went fine, you rename it to the original file.

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some gnu utils commands have a -i option (such as sed) that allow you to change a file in place .....most of file filtering and editing (like cut) can be done using sed.

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The shell will parse the command and handle the redirections first. When it sees "> afile" it will truncate "afile" and open it for writing. Your data is now destroyed. Then the shell hands the filename to cut which now has nothing to read.

This is how I learned:

some | pipeline < my_file > my_file.tmp
ln my_file my_file.bak   # this is a hard link
mv my_file.tmp my_file

That keeps the original data in place for as long as possible.

If you're having disk space issues, you will have to read the input file into memory entirely.

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In case of very limited disk space (disk quota) you could try to place a compressed source file in ram (/dev/shm) and use that as the source (uncompressing it to stdout and piping that to your script).