Run a command using arguments that come from an array

Question

Suppose I have a graphical program named app. Usage example: app -t 'first tab' -t 'second tab' opens two 'tabs' in that program.

The question is: how can I execute the command (i.e. app) from within a bash script if the number of arguments can vary?

Consider this:

#!/bin/bash tabs=( 'first tab' 'second tab' ) # Open the app (starting with some tabs). app  # ... How to get `app -t 'first tab' -t 'second tab'`? 

I would like the above script to have an effect equivalent to app -t 'first tab' -t 'second tab'. How can such a bash script be written?

Edit: note that the question is asking about composing command line arguments on the fly using an array of arguments.

Answer 1

Giving the arguments from an array is easy, "${array[@]}" expands to the array entries as distinct words (arguments). We just need to add the -t flags. To do that, we can loop over the first array, and build another array for the full list of arguments, adding the -t flags as we go:

#!/bin/bash tabs=("first tab" "second tab") args=() for t in "${tabs[@]}" ; do args+=(-t "$t") done app "${args[@]}" 

Use "$@" instead of "${tabs[@]}" to take the command line arguments of the script instead of a hard coded list.

Related: How can we run a command stored in a variable?

Answer 2

tabs=("-t" "one tab" "-t" "second tab") echo app "${tabs[@]}" app -t one tab -t second tab 

So now you should convert your original array to array with "-t" flags. Hope it's not a problem at all.

Answer 3

It's easier with zsh:

#!/bin/zsh - tabs=( 'first tab' 'second tab' ) app -t$^tabs 

That calls app as if you had entered:

app -t'first tab' -t'second tab' 

rc, es and fish do that implicitly (zsh's $^array is actually inspired from rc's ^):

In those shells,

app -t$tabs 

would do that as well. In zsh, you can get that behaviour as well by default by turning the rcexpandparam option on with set -o rcexpandparam.

In ksh93, bash and zsh, you can also use the ${array[@]/pattern/replacement} operator from ksh93:

#! /bin/bash - tabs=( 'first tab' 'second tab' ) app "${tabs[@]/#/-t}" 

Where we replace the (zero-width) start of each element with -t, so in effect prepending -t to each.

To call app as if with

app -t 'first tab' -t 'second tab' 

as opposed to

app -t'first tab' -t'second tab' 

That is where -t and first tab are two different arguments to app, with zsh:

app ${${:--t}:^^tabs} 

using the ${array1:^^array2}array-zipping operator where ${:--t} (minimal form of ${var:-default}) is used to inline the first array.

Answer 4

Basically the following bash script will read the file which include sites line by line and open each site in a new tab.

#!/bin/bash while read line do xdg-open "$line" done < /root/file 

Usage

./script.sh sites