8

Here is my script (to find the files that contain a specified pattern):

find . -type f \
    -exec awk -v vawk="$1" '/'"$vawk"'/ {c++} c>0 { print ARGV[1]; exit 0 } END { if (! c) {exit 1}}' \{\} \;

I would like to use my script with an argument §:

MyScript.sh pattern

My problem is that I don't manage to put the $1 variable in awk.

When I try to debug my script

bash -x MyScript.sh pattern

Here is the output :

+ find . -type f -exec awk -v vawk=pattern '// {c++} c>0 {print ARGV[1] ; exit 0 } END { if (! c) {exit 1}}' '{}' ';'

The $vawk variable seems to be empty.

Any idea?

7

You seem to be confusing awk variables and shell variables. awk -v vawk="$1" creates an awk variable called vawk, yet you are trying to use shell syntax ($vawk). This doesn't work because the shell doesn't have a variable called vawk. I think what you want is

awk -v vawk="$1" '$0 ~ vawk { c++ } # ...'
#                      ^ awk variable syntax
  • 1
    Note that awk expands the C-like escape sequences in $1, so that approach doesn't work if $1 may contain backslash characters (common for regexps). You may use the ENVIRON awk special array instead. – Stéphane Chazelas Apr 18 '17 at 12:27
6

Reproduced from this now closed as duplicate question as it includes warnings on the limitations of awk variable passing which one might find useful.

A shell variable is just that: a shell variable. If you want to turn it into a awk variable, you need a syntax such as:

awk -v x="$x" '$2 == x {print $1}' infile

or

awk '$2 == x {print $1}' x="$x" infile

However, those suffer from a problem: escape sequences are expanded in them.

So, for instance if the shell variable contains the two characters backslash and n, the awk variable will end up containing the newline character.

Another approach (but which like for -v requires a POSIX awk or nawk (as opposed to the 1970's awk still found as /bin/awk in Solaris)) is to use environment variables:

x="$x" awk '$2 == ENVIRON["x"] {print $1}' infile

Another approach (still with newer awks) is to use the ARGV array in awk:

awk 'BEGIN {x = ARGV[1]; delete ARGV[1]}
  $2 == x {print $1}' "$x" infile

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