[SOLVED]assigning "special" shell [variable] to awk, got problem

Question

$ VAR='AB' ; echo "$VAR" | awk -v foo="$VAR" '{gsub(foo,"Z");print}' # [1]
Z
$ VAR='[AB]' ; echo "$VAR" | awk -v foo="$VAR" '{gsub(foo,"Z");print}' # [2]
[ZZ]
$ VAR='[AB' ; echo "$VAR" | awk -v foo="$VAR" '{gsub(foo,"Z");print}' # [3]
awk: (FILENAME=- FNR=1) fatal: Unmatched [ or [^: /[AB/
$ VAR='AB]' ; echo "$VAR" | awk -v foo="$VAR" '{gsub(foo,"Z");print}' # [4]
Z
Just read about this:
Regular Expression Operators @ The GAWK Manual wrote:
    This is called a character set. It matches any one of the characters that are enclosed in the square brackets. For example:
    [MVX]
    matches any of the characters `M', `V', or `X' in a string.
And I tried,
$ echo "[AB]" | awk '{gsub(/\[AB\]/,"Z");print}' #[5]
Z
$ echo "[AB]" | awk '{gsub(/[AB]/,"Z");print}' #[6]
[ZZ]
[2] is behaving like [6] when I actually want it to be acting like [5].
What syntax should I use?
Last edited by lolilolicon (2009-08-16 10:58:28)

Answer 1

fumbles, I'm sorry I didn't explain myself clearly.
$ VAR='[AB]' ; echo "$VAR" | awk -v foo="$VAR" '{gsub(foo,"Z");print}'
outputs:
[ZZ] --> awk replaces each of A and B with Z, and left '[]' intact.
What I want is:
Z --> awk treats '[AB]' as a whole normal input, just like 'ABCD' or whatever...
Just like what I said, "[2] is behaving like [6] when I actually want it to be acting like [5]."
I need to do this because I'm writing a script where shell variable is assigned to awk variable, which contains '[]'. Like you said, awk is treating it as part of a regular expression...
EDIT:
Ok, an ugly solution::
$ VAR='[AB]'
$ VAR=$(echo "$VAR" | sed 's/\[/\\\\\[/;s/\]/\\\\\]/') #now VAR='\\[AB\\]'
$ echo "[AB]" | awk -v foo="$VAR" '{gsub(foo,"Z");print}'
Z
This almost sovles the problem I encountered in the script.
But there should be a better answer!
Say, is there a way to turn off awk's regular expression? --> Just found out grep's -F option. How about awk??
Last edited by lolilolicon (2009-08-16 08:42:36)