Bash – Extended file globbing not working with cat inside bash script

bashshellshell-scriptwildcards

When, in my terminal, I type

cat ~/my/+(a|b)/doc

It reads ok from both ~/my/a/doc and ~/my/b/doc, but when I put that command in a bash script:

#!/bin/bash
cat ~/my/'+(a|b)'/doc

I get the error:

cat: ~/my/+(a|b)/doc: No such file or directory

Is it not possible to use extended globbing inside a bash script?

Best Answer

You have to turn on extglob:

#!/bin/bash
shopt -s extglob
cat ~/my/+(a|b)/doc

+() is an extended pattern, is only recognized when extglob is enabled. By default extglob is on in interactive shells and off in non-interactive shells.

Related Solutions

Bash – Single-Quotes Parameter with Globbing Value

Try using arrays for your exclusions, and expand them into --exclude-dir and --exclude options.

e.g. in your ~/.codesearch_config script (presumably this is sourced by your main script?):

#! /bin/bash

# temporary array variables
declare -a __exclude_directories
declare -a __exclude_files

if [[ "$PWD" == "$HOME/project"* ]]; then
    __exclude_directories=(.git build tmp)
    __exclude_files=(translations)
elif [[ "$PWD" == "/some/where/else" ]]; then
    __exclude_directories=(foo bar)
    __exclude_files=(abc.txt def.txt xyz.txt)
fi

exclude_directories=''
exclude_files=''

for i in "${__exclude_directories[@]}" ; do
    exclude_directories+=" --exclude-dir '$i'"
done

for i in "${__exclude_files[@]}" ; do
    exclude_files+=" --exclude '$i'"
done

unset __exclude_directories
unset __exclude_files

# comment out or delete the next two lines after you've verified
# that the output is correct.
echo $exclude_directories 
echo $exclude_files

Later, you would use them like this:

out=$(grep -TInr$C$W --color=always \
      $exclude_files \
      $exclude_directories \
      "$SEARCH")

Note: there are no quotes around the $exclude_* variables here, otherwise they will be treated as a single argument each rather than multiple --exclude and --exclude-dir arguments. This is one of the very few situations where you do not want to and should not double-quote your variables (i.e. when you are constructing a command line in a variable or variables).

In almost all other cases, you should, as a matter of deeply-ingrained habit, double-quote your variables.

Bash Scripting – File Globbing Pattern Behaves Differently in Script

The !(...) Korn shell extended operator is only available in bash when you turn the extglob option on (it is off by default).

You may have extglob turned on in your interactive shell via ~/.bashrc or other initialization file, but notice that those files are not sourced when running scripts, and that option is not inherited from the calling shell (unless the BASHOPTS variable in the environment, but it would be a bad idea to have it there).

Explicitly turning it on with

shopt -s extglob

at the beginning of your script should work.

Notice that the shopt -s extglob only has effect beginning with the next line which wasn't already parsed. This means that you cannot use shopt -s extglob like set -f, to only turn the extended patterns on in a subshell:

# this won't work
(
  shopt -s extglob
  echo !(no such file)
)

You'd have to do something like:

(
  shopt -s extglob
  eval 'echo !(no such file)'
)

Best Answer

Related Solutions

Bash – Single-Quotes Parameter with Globbing Value

Bash Scripting – File Globbing Pattern Behaves Differently in Script

Related Question