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Old 07-10-2012, 02:01 AM   #1
Fracker
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Get Partition list one Liner Command


Hi guyz,

I have this command which normally serves my purpose, but I am sure there is better way to do it..

Code:
cat /proc/mounts | grep -v none | grep -v rootfs | grep -v proc | grep -v sys | grep -v /dev/root | awk '{print $2}' | grep -v /dev | grep -v nfs > tmpfil && while read i; do echo "Partition = $i"; done < tmpfil && rm -f tmpfil
I am doing some operation on all partitions (other then root and default ones).. here is what I cooked up, but don't look nice. Any help in doing this in more professional manner!

Last edited by Fracker; 07-10-2012 at 04:37 AM. Reason: Change Quote to Code
 
Old 07-10-2012, 02:41 AM   #2
David the H.
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First of all, please use ***[code][/code] tags*** around your code and data, to preserve formatting and to improve readability. Please do not use quote tags, colors, or other fancy formatting.


You have a Useless Use Of Cat and Grep, as well as unnecessary multiple instances of grep, even if you did need it (check out the -e option). The temp file and loop aren't necessary either.

A single awk command (it's a full text processing language that can completely replace grep and sed) with proper regex matching and formatted print statement can do it all. This command exactly replicates the above:

Code:
awk '( $0 !~ /none|rootfs|proc|sys|\/dev\/root/ && $2 !~ /\/dev|nfs/ ) { print "Partition = " $2 }' /proc/mounts
There may be cleaner ways to filter out the lines you want. All I did was re-write your posted code for awk.

Here are a few useful awk references:
http://www.grymoire.com/Unix/Awk.html
http://www.gnu.org/software/gawk/man...ode/index.html
http://www.pement.org/awk/awk1line.txt
http://www.catonmat.net/blog/awk-one...ined-part-one/

Here are a few regular expressions tutorials:
http://mywiki.wooledge.org/RegularExpression
http://www.grymoire.com/Unix/Regular.html
http://www.regular-expressions.info/

Last edited by David the H.; 07-10-2012 at 02:43 AM.
 
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Old 07-10-2012, 04:39 AM   #3
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Thanks, yeah that works great for text parsing. and also remove grep and cat mess.

I need loop or atleast a shell where I can play with normal shell commands. Awk don't have many commands. That's why I use while loop for this task.
 
Old 07-10-2012, 04:51 AM   #4
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Quote:
I need loop or atleast a shell where I can play with normal shell commands. Awk don't have many commands. That's why I use while loop for this task.
Please try and explain further so we might assist? Awk is a very full featured command / language and I would be surprised if what you need to accomplish cannot be handled.
 
Old 07-10-2012, 05:08 AM   #5
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Quote:
Originally Posted by grail View Post
Please try and explain further so we might assist? Awk is a very full featured command / language and I would be surprised if what you need to accomplish cannot be handled.
I need to assign single value to a variable and after that call a function, which will do some tasks based on this variable.

say

/tmp ---> xyz

func_somethingtodowithpartition

/var ---> xyz

func_somethingtodowithpartition

.
.
.
.

untill all partitions are done
 
Old 07-10-2012, 07:46 AM   #6
syg00
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I'll let you debate that one with the esteemed doyens above.

As an aside, what does any of this to do (directly) with partitions ... ?
 
Old 07-10-2012, 09:25 AM   #7
David the H.
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If you want to run arbitrary commands on the files, then you can still feed the raw output into a loop. For maximum safety regarding possible unusual filename characters, use a null separator between them ( use printf and "\0" in awk ).

How can I read a file (data stream, variable) line-by-line (and/or field-by-field)?
http://mywiki.wooledge.org/BashFAQ/001
How can I find and deal with file names containing newlines, spaces or both?
http://mywiki.wooledge.org/BashFAQ/020

Assuming bash, it's common to use a process substitution for this, instead of a pipe.
Code:
while IFS='' read -r -d '' mnt ; do

	echo "Partition = $mnt"
	mountlist+=( "$mnt" )

done < <( awk '( $0 !~ /none|rootfs|proc|sys|\/dev\/root/ && $2 !~ /\/dev|nfs/ ) { printf "%s\0", $2 }' /proc/mounts )
The second example command above adds the names to an array, so that they remain available for later in the script, if needed.

Last edited by David the H.; 07-10-2012 at 09:27 AM. Reason: small changes
 
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Old 07-10-2012, 10:48 AM   #8
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The other alternative is to call the action required within awk and use it to process the partitions.
Code:
awk '( !/none|rootfs|proc|sys|\/dev\/root/ && $2 !~ /\/dev|nfs/ ) { print | "ls " $2 }' /proc/mounts
Obviously you can change ls for your action.
 
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Old 07-11-2012, 12:09 AM   #9
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Thanks guyz for the great help, now I can compact the code as per requirements.
 
  


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