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mk1024
Asked: 2018-04-01 15:31:43 +0800 CST

Pass arguments from file line by line to function

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I have list of some mp3's:

song 1.mp3
song 2.mp3
.
.
.
song 349.mp3

I can see their bitrate via right mouse button -> Properties -> Audio/Video, but also I can check it using the terminal command 

file "song 1.mp3"

I'd like to find out which bitrate from my list is most frequently used, so I thought it would be nicely done via shell i.e. shell script.

I would lose too much time if I typed

file "song 1.mp3"; file "song 2.mp3"; ... ; file "song 349.mp3"

So, my question is :

Can we pass arguments line by line from some text file to shell function? An additional problem is that my song names contain spaces.

scripts command-line bash

2 Answers

  1. Assuming your list of files is one filename per line, the xargs utility should be able to handle filenames with spaces in them if you specify newline as the delimiting character e.g.

    xargs -d '\n' file < filelist.txt

    If you prefer to use a shell function

    while IFS= read -r f; do [[ -z "$f" ]] || file "$f"; done < filelist.txt
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  2. You can use a shell glob like *.mp3 to select all files in the current directory that end with .mp3. This will automagically take care of spaces and other special characters as well.

    On an mp3 I tested, I got output like this for file:

    01 - Mystery Of A Blood Red Rose.mp3:         Audio file with ID3 version 2.3.0, contains: MPEG ADTS, layer III, v1,  56 kbps, 44.1 kHz, Stereo

    You said you are interested in the bit rate, i.e. 56 kbps here. We can use grep to extract only that part of the output with a regular expression like '\d+\s+kbps' (one or more digits, followed by one or more spaces, followed by the string "kbps").

    So far, you can use this to show only the bit rate information for all mp3 files in the current directory:

    file *.mp3 | grep -Po '\d+\s+kbps'

    Now this produces a long list with one line per file, but you wanted a nice statistic with total counts. We can do that by sorting the list first (using natural number sort mode) and then counting how often each unique line appears. The tools for this are sort and uniq:

    file *.mp3 | grep -Po '\d+\s+kbps' | sort -n | uniq -c

    On one of my music folders, the output looked like below. First number is the file count, second the bit rate:

     16 32 kbps
 18 56 kbps
 67 128 kbps
  3 192 kbps
  6 256 kbps
 38 320 kbps
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