Equivalent regex in grep and sed of using not operator (!) in awk-CodePudding

Suppose I want to find a regular expression of this form:

awk '!/[^TAP]/ {print $1}' sample.txt

which gives matches for ATA, but not for ATAU, TAR and TR.

On the other hand this gives matches for all four of them:

awk '/[TAP]/ {print $1}' sample.txt

What is the correct regex syntax in grep and sed for the former case?

Mock input file is:

ATA
ATAU
TAR
TR

Output should be the line composed by a string containing only characters A and/or T and/or P, but not any other character.

CodePudding user response：

You may use this awk:

awk '/^[ATP] $/' file

ATA

Or this grep would also work:

grep '^[ATP]\ $' file

ATA

Regex pattern ^[ATP] $ will match one or more of A, T or P letters and due to anchors ^ and $, it won't allow any other character.