CODEWITHSUNDEEP
linuxparsingawkgrep
SD.
SD.

Reputation: 1500

Parse Linux command output

For command, amixer get PCM playback

I got output like this:

 "Simple mixer control 'PCM',0
  Capabilities: pvolume penum
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 255
  Mono:
  Front Left: Playback 255 [100%] [0.00dB]
  Front Right: Playback 255 [100%] [0.00dB]"

Now I need value "100%" in a variable; so, how can I parse it?

I am getting [100 with this:

amixer get PCM playback | grep "\[" | cut -d '%' -f1 | awk '{print $5}'

Upvotes: 0

Views: 4134

Answers (3)

Håkon Hægland
Håkon Hægland

Reputation: 40718

Using Gnu grep and Perl regex with positive lookahead and lookbehind, you can get the left-speaker value as

grep -Po '(?<=Left: Playback 255 \[)[^]]*(?=%\])'

Upvotes: 1

Jotne
Jotne

Reputation: 41456

Here is one way to do it.
Store left value in variable left

left=$(amixer get PCM playback | awk -F"[%[]" '/Left:/ {print $2}')


Store right value in variable right

right=$(amixer get PCM playback | awk -F"[%[]" '/Right:/ {print $2}')


Or store both data in in variable db

db=$(amixer get PCM playback | awk  -F"[%[]" '/dB/ {print $2}')
echo "$db"
100
100

Upvotes: 2

Jonathan Leffler
Jonathan Leffler

Reputation: 753615

First off, there are two 100% numbers in the sample output; which did you want? If they're always 100%, then you can simply assign var=100, so presumably they can sometimes be less than 100%.

It looks a bit like a case for sed, such as:

amixer get PCM playback | sed -n '/.*\[\([0-9]*\)%].*/s//\1/p'

The sed command should give you two numbers on two lines of output, with front left value preceding front right.

You collect the output from sed in a variable using Command Substitution:

playback=$(amixer get PCM playback | sed -n '/.*\[\([0-9]*\)%].*/s//\1/p')

This will give the two numbers in playback. You might prefer to use an array instead:

playback=( $(amixer get PCM playback | sed -n '/.*\[\([0-9]*\)%].*/s//\1/p') )

Now you can use:

left=0
right=1
echo "Left = ${playback[$left]}"
echo "Right = ${playback[$right]}"

This assumes you are using bash as your shell.

Upvotes: 3

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