How to correctly save the unix top command output into a variable?

Question

I've got to save the output of the top command into a variable and I do this:

myvar=`top -b -n1 | head -n 18`

The problem is that it seems to be ignoring the return characters, so when I echo the content of $myvar I see something like:

top - 15:15:38 up 745 days, 15:08, 5 users, load average: 0.22, 0.27, 0.32 Tasks: 133 total, 1 running, 132 sleeping, 0 stopped, 0 zombie Cpu(s): 6.4% us, 1.6%sy, 0.0% ni, 91.7% id, 0.3% wa, 0.0% hi, 0.0% si Mem: 2074716k total, 2038716k used, 36000k free, 84668k buffers Swap: 4192924k total, 107268k used, 4085656k etc...

How can I save all top data correctly?

Do you want to save it as a bash array? Is there a specific piece of data you need? and wouldn't it be easier to write to a tmp file? — Steve B.
– Steve B., Commented Jan 26, 2010 at 20:26

Greg Bacon · Accepted Answer · 2010-01-26 20:40:32Z

17

Notice the difference:

#! /bin/bash

x=`top -b -n 1 | head -n 5`
echo $x
echo --------------------
echo "$x"

Output:

top - 14:33:09 up 7 days, 5:58, 4 users, load average: 0.00, 0.00, 0.09 Tasks: 253 total, 2 running, 251 sleeping, 0 stopped, 0 zombie Cpu(s): 1.6%us, 0.4%sy, 70.3%ni, 27.6%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 3926784k total, 3644624k used, 282160k free, 232696k buffers Swap: 9936160k total, 101156k used, 9835004k free, 1287352k cached
--------------------
top - 14:33:09 up 7 days,  5:58,  4 users,  load average: 0.00, 0.00, 0.09
Tasks: 253 total,   2 running, 251 sleeping,   0 stopped,   0 zombie
Cpu(s):  1.6%us,  0.4%sy, 70.3%ni, 27.6%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   3926784k total,  3644624k used,   282160k free,   232696k buffers
Swap:  9936160k total,   101156k used,  9835004k free,  1287352k cached

Without the quotes, the contents of the variable are ground up in the shell's argument processing.

edited Jan 26, 2010 at 20:40

answered Jan 26, 2010 at 20:33

Greg Bacon

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1 Comment

Cristian Over a year ago

@gbacon thanks, it works fine like you say! I got it! Thanks everyone for reading and commenting.

Rob Wells · Accepted Answer · 2010-01-26 20:31:02Z

1

If you are looking for a particular piece of info within the top output i'd be inclined to filter the top output for what you're looking for before storing it rather than capture everything and then extract what you need.

answered Jan 26, 2010 at 20:31

Rob Wells

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Steve B. · Accepted Answer · 2010-01-26 20:35:57Z

-1

You could pipe it out through sed to catch and transform the line breaks, e.g.

top -n1 | sed 's/\(.*\)$/\1__CUSTOM_LINE_MARKER/g'

will output the CUSTOM_LINE_MARKER after every line. though Rob Wells answer above is probably a better approach.

answered Jan 26, 2010 at 20:35

Steve B.

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