Input

test:123456
smt:123456
test2:123456
mmm:123456
random:123456

Expected output

test:123456
test2:123456
random:1234567

CodePudding user response：

Soo many options:

$ awk -F':' 'length($1) != 3 {print}' <in.txt
test:123456
test2:123456
random:123456
$ sed  '/^...:/d' <in.txt
test:123456
test2:123456
random:123456
$ grep -v '^...:' <in.txt
test:123456
test2:123456
random:123456
$ python -c "import csv,sys; print('\n'.join([':'.join(a) for a in list(csv.reader(sys.stdin,delimiter=':')) if len(a[0]) != 3]))" <in.txt
test:123456
test2:123456
random:123456
$ perl -F: -nae 'length($F[0]) == 3 || print' <in.txt
test:123456
test2:123456
random:123456
$ ruby -F: -nae '$F[0].length == 3 || print' <in.txt
test:123456
test2:123456
random:123456
$

CodePudding user response：

There are many potential solutions to your problem. Without knowing what you've tried we can only guess which solutions might be appropriate. Because you've tagged bash, perhaps this will suit:

#!/bin/bash
while read -r line
do
    tmp="${line%%:*}"
    if [ "${#tmp}" -gt 3 ]; then
        echo "$line"
    fi
done < input.txt
test:123456
test2:123456
random:123456