Solved

How to Empty a File in a bash Shell Script

Posted on 2010-11-15
7
708 Views
Last Modified: 2012-05-10
The code is inside a loop that redirects output to a file. That file is then tested for whether it's empty or not. So, at the beginning of each iteration of the loop, I want to empty the file.

Can you tell me how to do that?

Something like this would be nice:

   FILE="$path/fileName"
   for ... do
      $FILE < EOF
      Other stuff...
      command 2> $FILE
      if $FILE not empty
          do something
      fi
   done
0
Comment
Question by:WizeOwl
7 Comments
 
LVL 26

Accepted Solution

by:
wilcoxon earned 350 total points
ID: 34141658
To empty a file, you can just do:

cp /dev/null $FILE
0
 
LVL 5

Assisted Solution

by:sandipshah
sandipshah earned 50 total points
ID: 34141667
Or delete the file and re-open it with the same name.

Ss
0
 
LVL 12

Assisted Solution

by:tel2
tel2 earned 100 total points
ID: 34141683
Or simply:

    >$FILE
0
Master Your Team's Linux and Cloud Stack!

The average business loses $13.5M per year to ineffective training (per 1,000 employees). Keep ahead of the competition and combine in-person quality with online cost and flexibility by training with Linux Academy.

 
LVL 84

Expert Comment

by:ozo
ID: 34141689
command 2> $FILE
will empty the file before it writes
0
 

Author Comment

by:WizeOwl
ID: 34141739
Thanks for all the suggestions.

1) cp /dev/null $FILE   >> is probably closest to what I was looking for.
2) Brute force is to delete and let first redirect "2>" create it when needed, again.
3) If ">$FILE" works, that may be most elegant.
4) command 2> $FILE doesn't help when testing loop iterations.
0
 
LVL 84

Expert Comment

by:ozo
ID: 34141773
command 2> $FILE doesn't help when testing loop iterations.
what are you testing that it doesn't help?
0
 

Author Closing Comment

by:WizeOwl
ID: 34141784
>$FILE does work
0

Featured Post

Master Your Team's Linux and Cloud Stack

Come see why top tech companies like Mailchimp and Media Temple use Linux Academy to build their employee training programs.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Email validation in proper way is  very important validation required in any web pages. This code is self explainable except that Regular Expression which I used for pattern matching. I originally published as a thread on my website : http://www…
Checking the Alert Log in AWS RDS Oracle can be a pain through their user interface.  I made a script to download the Alert Log, look for errors, and email me the trace files.  In this article I'll describe what I did and share my script.
Learn several ways to interact with files and get file information from the bash shell. ls lists the contents of a directory: Using the -a flag displays hidden files: Using the -l flag formats the output in a long list: The file command gives us mor…
Explain concepts important to validation of email addresses with regular expressions. Applies to most languages/tools that uses regular expressions. Consider email address RFCs: Look at HTML5 form input element (with type=email) regex pattern: T…

777 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question