"batch" files in bash

Question

I want to make a "batch" file so to say for some bash commands (convert.sh). I think it would be best to describe the situation. i have a $#!^ ton of mp4 videos that i want converted into mp3's. it would take me an unreasonable amount of time to convert them using ffmpeg -i /root/name\ of\ video.mp4 /name\ of\ video.mp3 for every single video. not to mention the fact that all the file names are long and complicated so typos are a possibility. so i want to know how to make a shell script (for bash) that will take every file with the extension .mp4 and convert it to a .mp3 with the same name one by one. as in it converts one then when it done it moves on to the next one. im using a lightweight version of linux so any 3rd part soft probably wont work so i need to use ffmpeg...

many thanks in advance for any assistance you can provide

PS: i cant seem to get the formatting sytax on the website to work right so if somone can format this for me and maybe post a link to a manual on how it works that would be much appreciated =)

PPS: i understand that questions about using the ffmpeg command should be asked on superuser however since i dont so much have any questions about the specific command and this relates more to scripting a bash file i figure this is the right place

There are formatting instructions in the sidebar on the edit/post page. You can also get help text by hovering over the tools. — Carl Norum, Feb 03 '13 at 17:58
Seems like you haven't taken a basic intro to shell scripting. Try googling "bash script tutorial" — Bjørne Malmanger, Feb 03 '13 at 18:01
@BjørneMalmanger see iv tried that kinda thing but all i can ever find is stuff on making directories and moving files..... — Konner Rasmussen, Feb 03 '13 at 18:16
Read http://www.tldp.org/LDP/abs/html/ (it does have imperfections, but it will teach you a lot); also learn about `at`, `batch`, `crontab`, `nohup`, `screen` .... commands — Basile Starynkevitch, Feb 03 '13 at 18:25
Also see the [FFmpeg MP3 Encoding Guide](https://ffmpeg.org/trac/ffmpeg/wiki/Encoding%20VBR%20%28Variable%20Bit%20Rate%29%20mp3%20audio). — llogan, Feb 04 '13 at 19:04

Carl Norum · Answer 1 · 2013-02-03T18:28:33.853

1

A bash for loop should do it for you in no time:

SRC_DIR=/root
DST_DIR=/somewhereelse
for FILE in ${SRC_DIR}/*.mp4
do
    ffmpeg -i "${FILE}" "${DST_DIR}/$(basename \"${FILE}\" .mp4).mp3"
done

Sorry - I don't know the ffmpeg command line options, so I just copied exactly what's in your post.

edited Feb 03 '13 at 18:28

answered Feb 03 '13 at 18:01

Carl Norum

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almost there... it gave me a problem with having sapces in the names.... said `/root/asr143: no such file or directory` – Konner Rasmussen Feb 03 '13 at 18:06
@Konner - I added some `""` in an edit that should fix that problem. – Carl Norum Feb 03 '13 at 18:07
1

Very nice... for some reason it gave me an issue with the -o option so i removed it and now am on my way to a seamless and pain free conversion =) thank you very much for you prompt and helpful response =) – Konner Rasmussen Feb 03 '13 at 18:25
Sorry, dunno where that -o came from. A quick glance at the ffmpeg docs says you don't need that. – Carl Norum Feb 03 '13 at 18:29
i spoke too soon (isnt that a wonderful thing) its trying to name all the files ".mp3" without the full names – Konner Rasmussen Feb 03 '13 at 18:51
Hmm... Add an `echo` in and start debugging I guess. Good luck! – Carl Norum Feb 03 '13 at 18:57
1

Instead of `basename` you can use [parameter expansion](http://mywiki.wooledge.org/BashFAQ/073). – llogan Feb 04 '13 at 19:02

score 1 · Answer 2 · edited May 23 '17 at 11:48

1) use find:

find . -name \*.mp4 | xargs ./my_recode_script.sh

2) my_recode_script.sh - see this question so you can easily change the extension for output file name

the rest is trivial scripting job:

ffmpeg -i $name $new_name # in my_recode_script.sh after changing extension

this is enough for one-time script, if you want something reusable, wrap it with yet another script which receive path to dir, extensions from which to which to recode and call other parts :)

"batch" files in bash

2 Answers2