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Is there a way to show the progress when running the cmp command?

Comparing large files or partitions using cmp can take a while.

I have searched google and used man cmp, but failed to find any useful information.

With the 'dd' command for example executing

kill -USR1 [pid_of_dd]

makes dd output its status in the console.

Is there a way to make cmp do something similar?

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migrated from Nov 23 '11 at 11:37

This question came from our site for professional and enthusiast programmers.

up vote 9 down vote accepted

You can use PipeViewer for this

pv firstfile | cmp -l secondfile > output
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Thanks! Your answer is really useful for other commandline stuff as well. – Iljaas Nov 24 '11 at 8:34
$ cmp -l firstfile secondfile &
[1] pid_of_cmp
$ ls -l /proc/pid_of_cmp/fd/
lrwx------ 1 user group 64 datetime 0 -> /dev/console
lrwx------ 1 user group 64 datetime 1 -> /dev/console
lrwx------ 1 user group 64 datetime 2 -> /dev/console
lr-x------ 1 user group 64 datetime 3 -> /path/to/firstfile
lr-x------ 1 user group 64 datetime 4 -> /path/to/secondfile
$ cat /proc/pid_of_cmp/fdinfo/0
pos:    25952256
flags:  0100000
$ cat /proc/pid_of_cmp/fdinfo/1
pos:    122650624
flags:  0100000

Compare pos to the size of the files.

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This option is very useful in some cases: you don't have the pv or bar commands; you don't have control over the command (for example a GUI program launches it); or the command doesn't support pipes. – golimar Feb 28 '13 at 17:59

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