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sedregex-group

Is there any way to match a string with only one character into character 'X' in sed?

I want to match all strings that have only one single character (including having with + or -) to turn into X but I get this output instead whenever I run it:

Xone     X
Xtwo     X
Xthree   X

Here's the file that I'm supposed to run with:

Cone      A-
Ctwo      D
Cthree    C+

Here's the code I've been working on:

code.sed

#!/bin/sed
s/[A-D][+-]/X/
s/[A-D]/X/

Desired output:

Cone      X
Ctwo      X
Cthree    X
Solution

  • Using a GNU sed, you can use

     sed -E 's/\b[[:upper:]]\b[+-]?/X/g'

    Details:

    • -E enables POSIX ERE syntax
    • \b - a word boundary
    • [[:upper:]] - an uppercase letter
    • \b - a word boundary
    • [+-]? - an optional + or -.

    See an online demo:

    s='Cone      A-
Ctwo      D
Cthree    C+'
sed -E 's/\b[[:upper:]]\b[+-]?/X/g' <<< "$s"

    Output:

    Cone      X
Ctwo      X
Cthree    X