Shell – How to simplify a conditional with multiple or statements

shell-script

I am writing a shell script that checks to see if a parameter matches a string. There are around 20 of them and more may need to be added in the future.

Currently the way I have it written it's hard to read and would be cumbersome to update. I'm not very familiar with shell scripting so I'm not sure of the best way to simplify this and make it easier to manage.

if [ $4 =="CRITICAL" ] && [[ $2 == "foo" || $2 == "bar" || $2 == "foo" || $2 == "bar" || $2 == "foo" || $2 == "bar" || $2 == "foo" || $2 == "bar" || $2 == "foo" || $2 == "bar" || ]]
  VARIABLE=1
fi

Foo and bar would all be different strings in the above script.

Best Answer

if [[ $4 == CRITICAL && $2 =~ ^(a|b|c|d|e|f|g)$ ]]; then
  VARIABLE=1
fi

BTW, unquoted variables and positional parameters are safe to use inside [[ ... ]], but not in [ ... ]. In other words, your [ $4 == "CRITICAL" ] should be [ "$4" == "CRITICAL" ].

Also, CRITICAL doesn't need to be quoted at all above . It's a fixed string, with no spaces or shell metacharacters. If it was a fixed string that did need quoting for any reason, it's best to use single quotes.

Single quotes are for fixed strings, double-quotes are for when you want to interpolate variables, command substitutions, etc into a string.

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Shell – How to perform the same set of commands within multiple subdirectories, in a numerical order

cd parent_directory/

for i in {-11..-10}
do
   for j in -2 0
   do
      (
      cd  "E${i}_G/E${j}_U/"
      ls -l ander ander.band ander.data
      cat ander.in
      cat ander.log
      pwd
      )
   done
done

Notes:

You can loop over a range of numbers by using the braces notation:
```
for i in {-11..-10}
```
You can also loop over an explicit list of items:
```
for j in -2 0
```
You can change the directory so some place that depends on variables:
```
cd  "E${i}_G/E${j}_U/"
```
The argument to the cd command is a directory specified relative to the current directory. After we have done our work in that directory, we want to change back to the parent_directory. There are many ways to deal with this but one simple way is to do that is to put the cd command and commands to be performed in that directory into a subshell, denoted by parens. After we exit the parens, the directory is automatically restored to what it was before.

Shell – Cycle between open windows with wmctrl

I've been long using a miniscript I named lonew for this. It's meant to be short for "lastof or new". lastof is another script of mine, which attempts to find a visible window that matches a given command a was accessed the most recently.

Both of the scripts are below:

(they might use some refactoring but they get the job done)

lonew:

#!/bin/bash
CMD="$1"; shift; ARGS="$@"
lastof $CMD || { echo $CMD $ARGS; $CMD $ARGS & }
disown

lastof:

#!/usr/bin/env ruby
#open-last
#List all windows and sort them by the time they were last accessed

require 'shellwords'

XTIME="_NET_WM_USER_TIME"

QARGV=ARGV.map {|arg| Shellwords.escape(arg)}

ids=IO.popen "xdotool search --onlyvisible #{QARGV.join(" ")}"
max_time_id=nil
max_time=nil

ids.each_line do |id|
  id.chomp!
  puts "id=#{id}"
  time=`xprop -id #{id} #{XTIME}`.split('=')[1].to_i

  max_time||=time
  max_time_id||=id
  if time > max_time
    max_time=time
    max_time_id=id
  end
end
exit(1) unless max_time_id
puts "Switching to ID: #{max_time_id}"
exit system("xdotool windowactivate #{max_time_id}")

__END__

Best Answer

Related Solutions

Shell – How to perform the same set of commands within multiple subdirectories, in a numerical order

Shell – Cycle between open windows with wmctrl

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