Is there a way we ask these kinds of question in plain english? and then have it return a snippet like this
There were efforts to do that for general programming; traces of those efforts survive today as COBOL and SQL.
Useful sed scripts and patterns
61–70 of 124 posts
Re: Useful sed scripts and patterns
#62Is there a way we ask these kinds of question in plain english? and then have it return a snippet like this
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Re: Useful sed scripts and patterns
#63There are a ton of little errors in this post (at the time of my leaving this comment, of course): the variable delimiter example is missing the close _, the first word example is missing the open ', and the except line 5 example is missing a space; meanwhile, these snippets will cause bad habits, such as thinking about "words" as "things involving letters", using -r instead of -E, and a massive knowledge gap with re…
Thank you for the feedback and the constructive criticism. Regarding the hold space I found it very confusing to use and understand. IMO it represents the 80/20 of sed (80% effort for 20% results). You're right, I'm using -r even when it's not necessary. To my defense I think it's a good habit to have since without it regex expressions are painful to write. I didn't considered that using -E it's a better choice but I…
Most examples that use '#!/bin/bash' should be rewritten to use '#!/usr/bin/sed -f'.
Example "multiple replacements":
#!/usr/bin/sed -f
s/a/A/
s/foo/BAR/
s/hello/HELLO/
Re: Useful sed scripts and patterns
#64There are a ton of little errors in this post (at the time of my leaving this comment, of course): the variable delimiter example is missing the close _, the first word example is missing the open ', and the except line 5 example is missing a space; meanwhile, these snippets will cause bad habits, such as thinking about "words" as "things involving letters", using -r instead of -E, and a massive knowledge gap with re…
100% agree.
This document shows practices of sed, but the author doesn't seem aware of best practices. A sed script starting with '#!/bin/bash' is a bad practice.
Re: Useful sed scripts and patterns
#65Mastering one tool is probably wise, but it's also good to know which tools may be better suited for some purposes. For "keep the first word of every line", I prefer awk: awk '{ print $1 }'
I agree with the people here saying that it's better to just use your favourite scripting language unless your job is mostly about writing little bash scripts like that (maybe sysops people?)... Here's a groovy script to do the same: new File('file.txt').eachLine { println it.split()[0] } Not as neat as awk, but not much worse either... and as I use Groovy a lot for testing, and its syntax is simplified Java (which I…
Use the best tool for the job.
sed is just a DSL (domain specific language) specifically designed for for manipulating text files line by line.
Note that for matching strings even in Groovy/AWK/Python/Perl/... you'll probably use regexp which are another DSL. Would you recommend to use string functions instead?
Re: Useful sed scripts and patterns
#66Remove csv header. sed 1d Select line 123 sed -n 123p # or sed -n 123{p;q}
sed -n '123{p;q;}'
Re: Useful sed scripts and patterns
#67This is awkward… I know it’s hip and cool to ask for donations, but for a tiny collection of sed scripts which aren’t including detailed explanations?
I feel like sed is what deserves the donation…
Re: Useful sed scripts and patterns
#68Earlier quoted context omitted.
I agree with the people here saying that it's better to just use your favourite scripting language unless your job is mostly about writing little bash scripts like that (maybe sysops people?)... Here's a groovy script to do the same: new File('file.txt').eachLine { println it.split()[0] } Not as neat as awk, but not much worse either... and as I use Groovy a lot for testing, and its syntax is simplified Java (which I…
In cases where it's a one time use, anything that gets you an answer easily is great. Could be Groovy, Ruby, Python, Perl, etc. or of course these bin tools. But if it's going to be used a lot, and start-up time matters, then some of the full programming languages can become expensive for the temporary load they create just spinning up. In those cases, the standard Unix tools tend to be so much faster and lighter tha…
Perl is much better than Pyhon for that for obvious reasons, Perl is like an improved sed with stereoids with some C inspiration.
Re: Useful sed scripts and patterns
#69Earlier quoted context omitted.
Thank you for the feedback and the constructive criticism. Regarding the hold space I found it very confusing to use and understand. IMO it represents the 80/20 of sed (80% effort for 20% results). You're right, I'm using -r even when it's not necessary. To my defense I think it's a good habit to have since without it regex expressions are painful to write. I didn't considered that using -E it's a better choice but I…
No mention of ';' to have multiple command on one line. Example: sed '10{p;q;}' myfile.txt
Thank you for your feedback! Personally I very rarely use the ; operator since it works badly with braces and commands that use files.
However I've added an example using the ; operator.
PS: May I humbly point out that the command you provided will actually print up to line 10 and then a duplicate line. Like I said, unexpected (even though it seems logical). :)
Re: Useful sed scripts and patterns
#70I understand the usefulness of this kind of command listing for people who just use sed occasionnaly and want to quickly copy/paste something still I think just learning how sed works is actually easier than treating it like magic. It's not awk . Sed is both logical and simple. Sed is the silent version of ed . It's a full line-oriented editor. You give it commands and it executes them on lines, one line at a time. C…
> I think just learning how sed works is actually easier than treating it like magic. It's not awk. As someone with over a decade of heavy sed use, who only got into awk recently, i'd say awk is far easier and less magical. Awk is just another programming language, for the most part. Using sed for anything substantial requires you to think in strange directions, to find ways to thread state and control flow through t…
I think I both agree and disagree.
As you rightfully pointed, I wouldn’t do anything overly complicated with sed because it really is a line editor and anything which is not line based and can’t be explained simply in the context of using an editor will quickly seem clunky and overly complicated.
I wouldn’t do anything period with awk. I agree with you that it’s just another programming language but one which feels extremely dated with both a terrible syntax and awkward semantics. The rare times I have encountered something done with awk it was either so simple it should have been done with sed or so complicated I wish a proper scripting language like python or perl would have been used instead. As far as I’m concerned, awk is a tool without a proper use-case. It’s always better to use something else.