CODEWITHSUNDEEP
linuxbashfunctionshellalias
Sopalajo de Arrierez
Sopalajo de Arrierez

Reputation: 3850

Linux shell scripting: Using alias in a function

I use an alias named ThousandsDotting that add points . each 3 numbers (the classic dot for thousands), so 100000 become 100.000.

It works fine in the shell, but not in a function. Example file example.sh:

#!/bin/bash 
function test() {
  echo "100000" | ThousandsDotting
}
alias ThousandsDotting="perl -pe 's/(\d{1,3})(?=(?:\d{3}){1,5}\b)/\1./g'"
test

If I run it, this is what I get:

$ ./example.sh
example.sh: line 3: ThousandsDotting: command not found.

What is the correct way to pipe (or use it without pipes, whatever) stdout data to this perl command in a function for my Bash shell script?

Upvotes: 2

Views: 655

Answers (4)

Mr Peach
Mr Peach

Reputation: 1364

Aliases are not expanded in bash and can't be used as macros. You can enable them, and for more information look at the eternal guide to BASH http://tldp.org/LDP/abs/html/aliases.html.

You can achieve the same as macros with the normal tools provided by bash:

#!/bin/bash
function test() {
    echo "100000" | perl -pe 's/(\d{1,3})(?=(?:\d{3}){1,5}\b)/\1./g'
}
test

You can improve this by making the function capable of having parameters: this way you can pass any argument to the function test obtaining exactly what you would have had by using an alias:

#!/bin/bash

function test() {
    perl -pe 's/(\d{1,3})(?=(?:\d{3}){1,5}\b)/\1./g' "$1"
}

test 100000

Upvotes: 0

Cyrus
Cyrus

Reputation: 88583

alias works in an interactive bash. Change

#!/bin/bash

to

#!/bin/bash -i

From man bash:

If the -i option is present, the shell is interactive.

Upvotes: 1

Hunter Zhao
Hunter Zhao

Reputation: 4649

Alias is limited by default in bash, so just enable it.

    #!/bin/bash

    shopt -s expand_aliases
    alias ThousandsDotting="perl -pe 's/(\d{1,3})(?=(?:\d{3}){1,5}\b)/\1./g'"
    function test() {
      echo "100000" | ThousandsDotting
    }
    test

output

100.000

Upvotes: 3

anubhava
anubhava

Reputation: 785068

In BASH Aliases are not inherited.

Better you create a function instead:

ThousandsDotting() { perl -pe 's/(\d{1,3})(?=(?:\d{3}){1,5}\b)/\1./g' "$1"; }

You can then use it as process substitution:

ThousandsDotting <(echo "100000")
100.000

Upvotes: 2

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