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Asked: 2014-07-21 02:26:15 +0800 CST

How to properly quote piped command for "watch"?

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I want to keep an eye on a file as it is created. So I used this command

ls -hal ./file |awk '{print $5}'

which gives the size of the file I am looking for. I use awk because I don't need other stuff, just the file size.

But I'm unable to use this with watch command, because if I try

watch ls -hal ./file |awk '{print $5}'

then watch only accepts ls -hal ./file and then pipes it to awk, giving no output.

If I try

watch "ls -hal ./file |awk '{print $5}'"

then it gets weird showing wrong command and whole output.

Every 2.0s: ls -hal ./file |awk '{print }'              Sun Jul 20 15:52:18 2014

-rw-rw---- 1 aditya aditya 1.7K Jul 20 15:52 ./file

You can see there is no $5 in the awk command.

Further quoting creates various similar errors.

So what is the right way to quote this command?

command-line

2 Answers

  1. Best Answer

    One option would be to escape the $ in your awk expression

    watch "ls -hal ./file |awk '{print \$5}'"

    Alternatively, you could avoid the issue altogether by using stat instead of parsing the output of ls

    watch stat -c '%s' ./file
    • 7

  2. Use following command :

    watch 'ls -hal ./file|cut -d " " -f 5'

    And if you want to highlight difference than,

    watch -d 'ls -hal ./file|cut -d " " -f 5'

    This will give work as you want!

    • 2