Relative "newbie" question about a a function call

Question

Level 1

60 points

Relative "newbie" question about a a function call

Hi all,
I am following along in "Learning Bash" and cannot get page 105 to work for me. (function call).
So, tried this little experiment, which leaves me stuck.
In the current directory, I have a script "myStack" as follows.

#! /bin/bash

test()
{
echo "Hello world"
}

I call it thus: (the current directory has been added to PATH)

myStack test

expecting to see "Hello World".

( Have tried myStack test(), also using a variety of quoting options)

I get no error, but get the prompt back with no text.

Anyone to the rescue?? 🙂

Thank you

Mac Pro, Mac OS X (10.6.5)

Posted on Jan 30, 2011 9:43 AM

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Answer 1

Jan 30, 2011 10:17 AM in response to pi22-7__

Your script doesn't do anything. It creates an internal function which is never called, then exits. The function is not a command-line argument, it is a re-usable piece of code for use inside the script. Call the function inside the script, like this:


#!/bin/bash
test() {
 echo "Hello world"
}
# Call the test function:
test

Or, another example that reuses the function:


#!/bin/bash
test() {
 echo "Goodnight, "$1
}
# Call the test function twice:
test world
test moon

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Answer 2

Linc Davis

Level 10

209,541 points

Jan 30, 2011 10:19 AM in response to pi22-7__

You don't call a function by passing it as an argument to the script. You have to call it from within the script; e.g.

test() { echo "Hello world" ; }
test

Also, "test" is a bad name for a function because it conflicts with a built-in command.

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Answer 3

BobHarris

Level 9

53,003 points

Jan 30, 2011 4:42 PM in response to pi22-7__

Side note. When posting code, you should wrap it in a pair of

tags

...
... your code here ...
...


The "myStatck test" invocation passes "test' as the $1 arg.
You can access your options via $1, $2, $3, $4, ...
$0 the path used to invoke your script
You can use 'shift' to remove $1, and shift $2 into $1, $3 into $2, etc...
You can substitute all the arguments at once using $* or "$*"
You can substitute all the arguments and preserve any command line quoting using "$@", where the double quotes are important.
You can loop through all your arguments using

for arg
do
echo "$arg"
done


There are other ways to loop though the arguments, for example

while [[ X$1 = X-* ]]
do
if [[ X$1 = X-q ]]; then
OPTION qSET=1
elif [[ X$1 = X-r ]]; then
OPTION rSET=1
elif [[ X$1 = X-s ]]; then
OPTION sSET=1
else
echo 1>&2 "Oops! Unknown option: $1"
exit 1
fi
shift # remove $1 so we can check the next argument
done

for arg
do
test "$arg"
done
exit 0
{code}

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Answer 4

pi22-7__ Author

Level 1

60 points

Jan 30, 2011 8:00 PM in response to BobHarris

Thank you all who answered and helped me understand the issue better. Bob, you put it in context for me, which is what I realized I was after from the beginning.

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