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hpr2679 :: Extra ancillary Bash tips - 13

Making decisions in Bash (part 5)

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Hosted by Dave Morriss on 2018-11-08 is flagged as Explicit and is released under a CC-BY-SA license.
Tags: Bash,extended test,regular expression,capture group,BASH_REMATCH,back reference.
Listen in ogg, spx, or mp3 format. | Comments (2)

Part of the series: Bash Scripting

This is an open series in which Hacker Public Radio Listeners can share their Bash scripting knowledge and experience with the community. General programming topics and Bash commands are explored along with some tutorials for the complete novice.

Extra ancillary Bash tips - 13

Making decisions in Bash

This is the thirteenth episode in the Bash Tips sub-series. It is the fifth and final of a group of shows about making decisions in Bash.

In the last four episodes we saw the types of test Bash provides, and we looked briefly at some of the commands that use these tests. We looked at conditional expressions and all of the operators Bash provides to do this. We concentrated particularly on string comparisons which use glob and extended glob patterns then we devoted an episode to Bash regular expressions.

Now we want to look at the final topic within regular expressions, the use of capture groups.

Long notes

I have provided detailed notes as usual for this episode, and these can be viewed here.


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Comment #1 posted on 2018-11-24T17:12:57Z by clacke

Immediately useful

Very good episode about some functionality I always vaguely knew was there, but never considered using or even looking into.

Lo and behold, within a week after listening to it, I have already made use of my new-found knowledge to parse some predictably-formatted JSON!

I ran into issues with quoting the expression, and worked around them by assigned the expression to a variable and referring to that variable in the conditional.

Now I'm listening to #2669, and I understand exactly why it went wrong.

For the sake of readability, I actually think the assignment workaround was the best way to express it.

Comment #2 posted on 2018-11-25T19:56:03Z by Dave Morriss

Thanks clacke!

Glad you found the show(s) useful and are using Bash regular expressions and capture groups.

Parsing JSON with Bash is a challenging task to take on though, I use jq to do this myself - or the JSON module in Perl of course ;-)

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