CODEWITHSUNDEEP
bashawkgrepoutput
KuboMD
KuboMD

Reputation: 684

Bash Output Dropped?

Here's my code. It's basically just grep'ing and making the output look nicer. It works just fine, however if I use REGEX input the output is blank. The "myVar" which counts the # of grep lines returned seems to be correct, but it seems like awk is losing the output text.

Thanks.

#!/bin/bash
center() {
  termwidth="$(tput cols)"
  padding="$(printf '%0.1s' ={1..500})"
  printf '%*.*s %s %*.*s\n' 0 "$(((termwidth-2-${#1})/2))" "$padding" "$1" 0 "$(((termwidth-1-${#1})/2))" "$padding"
}

if [ $1 = "-h" ] || [ $# -eq 0 ]; then
        echo 'USAGE: ./Check.sh [PATTERN1] [PATTERN2] [PATTERN3] ... [PATTERN20]
Search for PATTERN in the HOSTS file. Patterns can be in the Perl REGEX form.'
else
        for item in "$@"
          do
          center "SEARCHING $item"
          grep -i $item /etc/hosts
          myVar=$(wc -l <(grep -i -P $item /etc/hosts) | awk '{print $1}')
          if [ $myVar -eq 0 ]; then
                center "COULD NOT FIND $item"
          fi
          center "FOUND $myVar IN $item"
        done
fi

OUTPUT:

$ ./Check.sh '^142.[0-9]+'
=================================================================== SEARCHING ^142.[0-9]+ ===================================================================
================================================================= FOUND 945 IN ^142.[0-9]+ ==================================================================
$ cat /etc/hosts | grep -i -P -c '^142.[0-9]+'
945

If I input a non-regex string the output and count are both fine. The file being grep'ed is a corporate host file so I can't share successful output, but basically the matched lines go between the "SEARCHING" and "FOUND" line.

Upvotes: 0

Views: 52

Answers (1)

Charles Duffy
Charles Duffy

Reputation: 295345

It's not that content from the first grep is being dropped somehow (which is impossible without terminal control characters clearing the screen or moving the cursor upwards, as that output was already sent to the terminal before awk is started). Rather, the second grep is being run with different arguments, such that only the grep whose output goes to wc -l and then to awk is parsing its argument as a PCRE-style regex at all.

Change:

grep -i $item /etc/hosts

To:

grep -i -P "$item" /etc/hosts

Upvotes: 1

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