How to clear the contents of a file from the command line?

I have a log file that has a bunch of stuff in it that I don't need anymore. I want to clear the contents.

I know how to print the contents to the screen:

cat file.log

I know how to edit the file, line-by-line:

nano file.log

But I don't want to delete each line one at a time. Is there a way to do it in one command without destroying the file to do it?

18 Answers

In bash, just

> filename

will do. This will leave you with an empty file filename.

PS: If you need sudo call, please consider to use truncate as answered here.

4

You can use the user command : truncate

truncate -s 0 test.txt

("-s 0" to specify the size)

5

You could do this:

echo -n "" > file.log

Using > to write the (null) input from echo -n to the file.

Using >> would append the null input to the file (effectively doing nothing but touching it).

5

: > file.log

Same as > filename in Bash, but works in more shells (credit). Redirects the output from the true builtin (which has no output) to filename.

2

ZSH

>! filename

ZSH will protect users from clobbering files using the io redirect operator >. If you use >! you can force the truncation of an existing file.

If you want ZSH to use Bash's redirection behavior, were there is no protection from file clobbering, then you need to set the clobber option for your shell.

More Info:

IF you want to do from inside a vim editor in command line, you can try this:

vim file.txt 

Press Esc.

:1,$d

Press Enter.

You will find all lines deleted.

2

Below command should also work :

cat /dev/null > file.log

2

$ rm file.log; touch file.log

or

$ cat > file.log

followed by control-d.

or...or...or...

Ah. Here is a single command version:

$ dd if=/dev/null of=file.log

5

If you need to sudo to superuser privilege to access the file then the accepted answer will not work. Using this does work:

truncate -s0 file

or explicitly with sudo:

sudo truncate -s0 file

More info here

It can be done using sed

sed -i d filename

2

Few alternatives:

ex +%d -scwq file.log
cp /dev/null file.log
vi +%d -escwq file.log
install -m600 /dev/null file.log

If you have spaces in filenames, use:

for file in /path/to/file/*; do > "$file"; done

(I could not to include it in comments to previous answer because I don't have 50 reputation. Sometimes limitations are contra productive.)

There are multiple ways to clear the file as listed below:

echo "" > filename
cat /dev/null > filename

Below examples are mostly used in shell scripting

just# > filename
: > filename

One line at a time?

Try vi(m), the lovely text editor that can do anything. In this case, navigate to a line, press d (for delete), and d again (for line).

2

With my permissions this is the only thing that worked:

touch temp.txt
sudo mv temp.txt original-file.txt

Also, if you have multiple files you can use the following:

for file in /path/to/file/*; do > $file; done

This is helpful for log files in the same directory.

In windows environment:

type nul >filename

here is some test i have done: cat test cp test test.bkp cat /dev/null > test

This will empty the original test and but you can still access the test.bkp if you need the old contents of the file.

1