Ubuntu – Emptying the contents of a text file

command line

I have a text file in my home directory which receives data regularly through a cron job. Because the cron job provides dynamic data, I would also want to set a cron job to empty the file contents (the file must still exist). I don't need help with cron, just the command which can help with emptying the file.

Best Answer

The simplest way:

> filename

This is a less obvious way and probably less readable in a shell script by others, but it's all you need.

Because > is not actually a really command (it is bash builtin) you can't use:

sudo > filename

when you don't have permissions on that file. But you can use:

sudo bash -c "> filename"

Related Solutions

Ubuntu – Find and report line numbers of empty lines in text file

You can find the empty lines, and their line numbers, with

grep -E --line-number --with-filename '^$' file.txt

An example:

w3@aardvark:~(0)$ grep -E --line-number --with-filename '^$' file.txt
file.txt:1:
file.txt:3:
file.txt:4:
w3@aardvark:~(0)$ cat -n file.txt
     1  
     2  Not empty
     3  
     4  
     5  Not empty
w3@aardvark:~(0)$

If your "empty" lines contain blanks or TABs, use:

grep -E --line-number --with-filename '^\s*$' file.txt

Best Answer

Related Solutions

Ubuntu – Find and report line numbers of empty lines in text file

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