How to replace text in a specific line between first appearence of a symbol and second appearence of it

Question

So, let's say I have some text file like this:
aaaa:bbbb:cccc:dddd
eeee:ffff:gggg:hhhh
iiii:jjjj:kkkk:llll

and I need a command that makes me able to replace what is in between the first and second : in a variable line.
I managed to do something like this but it's obviously just adding the text in the middle: sed $lineNumber' s/:/:'$pass'/' users.txt
the result given by the command should be someting like this if I want to replace what is in between the first and second ":" of the second line with "asd"
aaaa:bbbb:cccc:dddd
eeee:asd:gggg:hhhh
iiii:jjjj:kkkk:llll

Cyrus · Answer

A job for awk:
awk -v col="2" -v row="2" -v sep=":" -v new="asd" 'BEGIN{FS=OFS=sep} NR==row{$col=new} {print}' file

or
awk 'NR==row{$col=new}1' col='2' row='2' FS=':' OFS=':' new='asd' file

Output:

aaaa:bbbb:cccc:dddd
eeee:asd:gggg:hhhh
iiii:jjjj:kkkk:llll

See: 8 Powerful Awk Built-in Variables – FS, OFS, RS, ORS, NR, NF, FILENAME, FNR

webb · Answer

Use a regular expression that matches the entire part that you want to replace, e.g.,
sed "$lineNumber s/:[^:]+/:$pass/" users.txt
#                   ^^^^^^ = not : one or more times

Kent · Answer

if you want shell variables to get expanded, use double quotes in sed command:
sed "$var1 s/:/:$var2/" file

How to replace text in a specific line between first appearence of a symbol and second appearence of it

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