How to create a function

GPGAgent · 07-28-2019, 06:10 PM

I use this code in my bash scripts to prompt for input:

Code:

default="60-80"
read -e -p "Gap in Seconds between cuts [${bold}$default${norm}]: " GAP_SPAN
GAP_SPAN=${GAP_SPAN:-$default}

How can I turn this into a function?

I tried this but it doesn't work:

Code:

# Usage: x=$( ReadInput "Output Extension [${bold}$default${norm}|mpg|avi]: " "*.mp4" )
function ReadInput { 
default="$2"
read -p "$1" "$2"
echo ${x:-$default}
}

And I called it later in the same script like this:

Code:

...
..
...
bold=$(tput bold)
norm=$(tput sgr0)

FF=$( ReadInput "Output Extension [${bold}$default${norm}|mpg|avi]: " "mp4" )
echo $FF
..
...
..

And also it doen't bold face the default value

rtmistler · 07-28-2019, 06:44 PM

You don't need the word function.

I have an example of functions in the same file as the main part of the script in the blog about bash programming in my signature. There is a section specifically about functions.

berndbausch · 07-28-2019, 08:36 PM

Quote:

Originally Posted by GPGAgent

I tried this but it doesn't work:

Can you be more specific? How did you test it? Does it issue an error message? In which way does it behave differently than expected?

BW-userx · 07-28-2019, 10:32 PM

Quote:

Originally Posted by GPGAgent

I use this code in my bash scripts to prompt for input:

Code:

default="60-80"
read -e -p "Gap in Seconds between cuts [${bold}$default${norm}]: " GAP_SPAN
GAP_SPAN=${GAP_SPAN:-$default}

How can I turn this into a function?

I tried this but it doesn't work:

Code:

# Usage: x=$( ReadInput "Output Extension [${bold}$default${norm}|mpg|avi]: " "*.mp4" )
function ReadInput { 
default="$2"
read -p "$1" "$2"
echo ${x:-$default}
}

And I called it later in the same script like this:

Code:

...
..
...
bold=$(tput bold)
norm=$(tput sgr0)

FF=$( ReadInput "Output Extension [${bold}$default${norm}|mpg|avi]: " "mp4" )
echo $FF
..
...
..

And also it doen't bold face the default value

minus some error checking and all the bells and whistles.

Code:

#!/bin/bash

usage()
{
	echo "
	Enter two prams in seconds 
	$0 <pram> <pram> "
	
}
getPrams()
{
	
	[[ "$#" -ne 2 ]] &&
	{ echo " I need two prams yo!" ; usage ;  exit ; }
	
	GAP_SPAN=$1-$2
}

getPrams2()
{
	GAP_SPAN="GAP_SPAN=$sec1-$sec2"
}

getPrams $1 $2

echo "GAP_SPAN=$GAP_SPAN"

read -p "I need two prams for seconds " sec1 sec2

echo "$sec1 $sec2"

getPrams2

echo $GAP_SPAN

Two different ways to get information off the CLI and pass it into a function.
should give you an Idea of something.

pan64 · 07-29-2019, 04:01 AM

interesting (at least for me): using this small script:

Code:

#!/bin/bash

bold="$(tput bold)"
norm="$(tput sgr0)"

function ReadInput { 
    default="$2"
    read -p "$1" "$2"
    echo ${x:-$default}
}

ReadInput "Output Extension [${bold}$default${norm}|mpg|avi]: " "mp4"
ReadInput "Output Extension [${bold}$default${norm}|mpg|avi]: " "mp4"

I will get the following result:

Code:

user@host:/tmp$ ./a.sh
Output Extension [|mpg|avi]: 
mp4
Output Extension [mp4|mpg|avi]: 
mp4
user@host:/tmp$

that means the first invocation did not work properly, but the second.

I don't know if this is the original issue (OP should tell us) and if it was reproducible at all.

GPGAgent · 07-29-2019, 09:29 AM

Quote:

Originally Posted by berndbausch

Can you be more specific? How did you test it? Does it issue an error message? In which way does it behave differently than expected?

Ahh, yes I should have said how it doesn't work - here goes:

Code:

charlie@charlie-machine:~$ 000-Skeleton.sh 
10761 (process ID) old priority 0, new priority 19
 from function - Output Extension [|mpg|avi]: MP4
FF: mp4 <=== Output here
from body - Output Extension [mp4|mpg|avi]: MP4
OUTPUTEXTENSION: MP4 <=== Output here

See the attached image as well

1 The function doesn't display the default value - it should be mp4 and in bold face

2 I entered MP4, the function returned mp4

The code in the body performs as I expected

GPGAgent · 07-29-2019, 09:40 AM

Quote:

Originally Posted by pan64

interesting (at least for me): using this small script:

Code:

#!/bin/bash

bold="$(tput bold)"
norm="$(tput sgr0)"

function ReadInput { 
    default="$2"
    read -p "$1" "$2"
    echo ${x:-$default}
}

ReadInput "Output Extension [${bold}$default${norm}|mpg|avi]: " "mp4"
ReadInput "Output Extension [${bold}$default${norm}|mpg|avi]: " "mp4"

I will get the following result:

Code:

user@host:/tmp$ ./a.sh
Output Extension [|mpg|avi]: 
mp4
Output Extension [mp4|mpg|avi]: 
mp4
user@host:/tmp$

that means the first invocation did not work properly, but the second.

I don't know if this is the original issue (OP should tell us) and if it was reproducible at all.

I tried that and this is what resulted:

The code:

Code:

#!/bin/bash
renice 19 -p $$

# Usage: x=$( ReadInput "Output Extension [${bold}$default${norm}|mpg|avi]: " "*.mp4" )
function ReadInput { 
default="$2"
read -p "$1" "$2"
echo ${x:-$default}
}


bold=$(tput bold)
norm=$(tput sgr0)

FF=$( ReadInput " from function - Output Extension [${bold}$default${norm}|mpg|avi]: " "mp4" )
echo "FF: $FF <=== Output here"

FF=$( ReadInput " from function - Output Extension [${bold}$default${norm}|mpg|avi]: " "mp4" )
echo "FF: $FF <=== Output here"

default="mp4"
read -p "from body - Output Extension [${bold}$default${norm}|mpg|avi]: " OUTPUTEXTENSION
OUTPUTEXTENSION=${OUTPUTEXTENSION:-$default}
echo "OUTPUTEXTENSION: $OUTPUTEXTENSION <=== Output here"

exit 99

Code:

charlie@charlie-machine:~$ 000-Skeleton.sh 
11294 (process ID) old priority 0, new priority 19
 from function - Output Extension [|mpg|avi]: 99
FF: mp4 <=== Output here
 from function - Output Extension [|mpg|avi]: 99
FF: mp4 <=== Output here
from body - Output Extension [mp4|mpg|avi]: 99
OUTPUTEXTENSION: 99 <=== Output here
charlie@charlie-machine:~$

and see attached image

Thanks for looking
The output:

pan64 · 07-29-2019, 09:54 AM

yes, that is a bit different. I don't understand it at this moment, but will try to find an explanation.

GPGAgent · 07-29-2019, 10:35 AM

Quote:

Originally Posted by rtmistler

You don't need the word function.

I know, I just prefer it this way, and great blog as well