I'm trying to strip the version out of a package name using only Bash. I have one solution but I don't think that's the best one available, so I'd like to know if there's a better way to do it. by better I mean cleaner, easier to understand.
suppose I have the string "my-program-1.0" and I want only "my-program". my current solution is:
#!/bin/bash
PROGRAM_FULL="my-program-1.0"
INDEX_OF_LAST_CHARACTER=`awk '{print match($0, "[A-Za-z0-9]-[0-9]")} <<< $PROGRAM_FULL`
PROGRAM_NAME=`cut -c -$INDEX_OF_LAST_CHARACTER <<< $PROGRAM_FULL`
actually, the "package name" syntax is an RPM file name, if it matters.
thanks!
Pretty well-suited to sed:
# Using your matching criterion (first hyphen with a number after it
PROGRAM_NAME=$(echo "$PROGRAM_FULL" | sed 's/-[0-9].*//')
# Using a stronger match
PROGRAM_NAME=$(echo "$PROGRAM_FULL" | sed 's/-[0-9]\+\(\.[0-9]\+\)*$//')
The second match ensures that the version number is a sequence of numbers separated by dots (e.g. X, X.X, X.X.X, ...).
Edit: So there are comments all over based on the fact that the notion of version number isn't very well-defined. You'll have to write a regex for the input you expect. Hopefully you won't have anything as awful as "program-name-1.2.3-a". Absent any additional request from the OP though, I think all the answers here are good enough.
Bash:
program_full="my-program-1.0"
program_name=${program_full%-*} # remove the last hyphen and everything after
Produces "my-program"
Or
program_full="alsa-lib-1.0.17-1.el5.i386.rpm"
program_name=${program_full%%-[0-9]*} # remove the first hyphen followed by a digit and everything after
Produces "alsa-lib"
How about:
$ echo my-program-1.0 | perl -pne 's/-[0-9]+(\.[0-9]+)+$//'
my-program
Related
So I think I've cracked the regex but just can't crack how to get sed to make the changes. I have a variable which is this:
MAKEVAR = EPICS_BASE=$CI_PROJECT_DIR/3.16/base IPAC=$CI_PROJECT_DIR/3.16/support/ipac SNCSEQ=$CI_PROJECT_DIR/3.16/support/seq
(All one line). But I want to delete the particular section defining IPAC so my regex looks like this:
(IPAC.+\s)
I know from using this tool that that should be correct:
https://www.regextester.com/98103
However when I run different iterations of trying out sed like:
sed 's/(IPAC.+\s)/\&/g' <<< "$MAKEVAR"
And then echo out MAKEVAR, the IPAC section still exists.
How can I update a particular section of text in a shell variable to remove a section beginning with IPAC up until the next space?
Thanks in advance
regextester (or any other online tool) is a great way to verify that a regexp works in that online tool. Unfortunately that doesn't mean it'll work in any given command-line tool. In particular your regexp includes \s which is specific to PCREs and some GNU tools, and uses (...) to delineate capture groups but that's only used in EREs and PCREs, not BREs such as sed supports by default where you'd have to use \(...\), and your replacement text is using '&' which is telling sed you want to replace the string that matches the regexp with a literal \& when in fact you just want to remove it.
This is how to do what I think you're trying to do using any sed:
$ sed 's/IPAC[^ ]* //' <<< "$MAKEVAR"
EPICS_BASE=$CI_PROJECT_DIR/3.16/base SNCSEQ=$CI_PROJECT_DIR/3.16/support/seq
Nevermind, found a workaround:
MAKEVAR=$(sed -E 's/(IPAC.+ipac)//' <<<"$MAKEVAR")
Use a shorter
MAKEVAR=$(sed 's/IPAC.*ipac//' <<< "$MAKEVAR")
IPAC.*ipac matches all the way from first IPAC to last ipac. The matched text is removed from the text.
I did check the ABS, but it was hard to find a reference to my problem/question there.
Here it is. Consider the following code (Which extracts the first character of OtherVar and then converts MyVar to uppercase):
OtherVar=foobar
MyChar=${OtherVar:0:1} # get first character of OtherVar string variable
MyChar=${MyChar^} # first character to upper case
Could I somehow condense the second and third line into one statement?
P.S.: As was pointed out below, not needs to have a named variable. I should add, I would like to not add any sub-shells or so and would also accept a somehow hacky way to achieve the desired result.
P.P.S.: The question is purely educational.
You could do it all-in-one without forking sub-shell or running external command:
printf -v MyChar %1s "${OtherVar^}"
Or:
read -n1 MyChar <<<"${OtherVar^}"
Another option:
declare -u MyChar=${OtherVar:0:1}
But I can't see the point in such optimization in a bash script.
There are more suitable text processing interpreters, like awk, sed, even perl or python if performance matters.
You could use the cut command and put it in a complex expression to get it on one line, but I'm not sure it makes the code too much clearer:
OtherVar=foobar
MyChar=$(echo ${OtherVar^} | cut -c1-1) # uppercase first character and cut string
I need help with a sed expression to find a # immediately followed by x numbers... I can't figure it out.
eg.
[Issue #40] or [Issue #210]
I need to match the #xx or #xxx pattern so I can perform a substitution on it.
Been so long since I've done any of this stuff =|
If you need to match digits immediately following a pound symbol, this should work:
/#[0-9]+/
As for the sed implementation or shell program implementation (e.g. awk), it's too hard to provide an example from your question. Here's a vague attempt...
sed -E 's/#[0-9]+/<replacement>/' </tmp/file.log
sed 's/#[0-9]*/foo/'
MIGHT be what you want but since you haven't provided anything we can test against it's a guess...
From your comments you might want:
sed -E 's/#[0-9]+/foo/'
but that might match other things you don't want to match too, idk, it all depends what the input you haven't shown us contains.
I'm writing some automation for getting perticular path, I got the code, but I'm unable to understand what exactly the below commands does?
sed 's;//;/;g'
egrep "\-example (|\:)$variablename:"
In sed, it is common to use / as a delimiter for the s command, but any character will do and it is common to choose a character that does not appear in either the pattern or the replacement. In this case, ; was chosen as the delimiter. This command is simply replacing occurrences of // with /. It is equivalent to the (IMO) more readable :s#//#/#g
The egrep is a syntax error which perhaps should have been written: egrep "-example (:)?$variablename:", which will match text with or without the :. (That is, if variablename=foo, then this will match either -example foo: or -example :foo:. That may not be what is intended, but it's hard to say since the given example is not valid syntax. It appears to want to provide alternatives between a : or something else, but the alternative is missing.)
I am writing a shell (bash) script and I'm trying to figure out an easy way to accomplish a simple task.
I have some string in a variable.
I don't know if this is relevant, but it can contain spaces, newlines, because actually this string is the content of a whole text file.
I want to replace the last occurence of a certain substring with something else.
Perhaps I could use a regexp for that, but there are two moments that confuse me:
I need to match from the end, not from the start
the substring that I want to scan for is fixed, not variable.
for truncating at the start: ${var#pattern}
truncating at the end ${var%pattern}
${var/pattern/repl} for general replacement
the patterns are 'filename' style expansion, and the last one can be prefixed with # or % to match only at the start or end (respectively)
it's all in the (long) bash manpage. check the "Parameter Expansion" chapter.
amn expression like this
s/match string here$/new string/
should do the trick - s is for sustitute, / break up the command, and the $ is the end of line marker. You can try this in vi to see if it does what you need.
I would look up the man pages for awk or sed.
Javier's answer is shell specific and won't work in all shells.
The sed answers that MrTelly and epochwolf alluded to are incomplete and should look something like this:
MyString="stuff ttto be edittted"
NewString=`echo $MyString | sed -e 's/\(.*\)ttt\(.*\)/\1xxx\2/'`
The reason this works without having to use the $ to mark the end is that the first '.*' is greedy and will attempt to gather up as much as possible while allowing the rest of the regular expression to be true.
This sed command should work fine in any shell context used.
Usually when I get stuck with Sed I use this page,
http://sed.sourceforge.net/sed1line.txt