Question

8

Why some user functions don't get recognised by bash?

rated 0 times [ 8] [ 0] / answers: 1 / hits: 11769 / 3 Years ago, fri, october 22, 2021, 9:27:09

I can define a function like:

myfunction () { ls -R "$1" ; }

And then

myfunction .

just works.

But if I do

echo "myfunction ." | sh

echo "myfunction ." | bash

the messages are:

sh: myfunction: not found  

bash: line 1: myfunction: command not found

Why? And how can I call a function that comes from a string if not by piping it to sh or bash?

I know there is this command source, but I am confused of when I should use source and when sh or bash. Also, I cannot pipe through source. To add to confusion, there is this command . that seems to have nothing to do with the "." that means "current directory".

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

cocal

Add To Favorites

Follow

Total Points: 236

Total Questions: 111

Total Answers: 123

Location: Belarus

Member since Tue, Mar 14, 2023

1 Year ago

cocal questions

1 Cannot change opacity of Dock in 22.04

Tue, Oct 12, 21, 20:46, 3 Years ago

1 Pin messages to stay always on top with Thunderbird

Sat, Oct 8, 22, 04:23, 2 Years ago

1 Bash CLI: Restore previously typed command after changing it

Wed, Sep 14, 22, 22:38, 2 Years ago

1 100% battery show as 71%

Sun, Dec 18, 22, 02:24, 1 Year ago

1 Desktop larger than the screen

Wed, Jun 29, 22, 17:31, 2 Years ago

View All

answered 3 Years ago diffeah · Accepted Answer

A function definition only has an effect in the current instance of bash. When you write

echo "myfunction ." | bash

you run another instance of bash. You would need to define the function in that other instance.

If you have a string that contains a function name and arguments (quoted, if necessary), or more generally any string that contains some shell source code that you want to execute, use the eval builtin.

my_snippet='myfunction .'

eval "$my_snippet"

If you define functions in your .bashrc, they are only available in interactive shells, not in scripts.

The . command is (almost) equivalent to source, and has nothing to do with . meaning the current directory.