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Aliases NOT working inside bash shell script

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Top Forums Shell Programming and Scripting Aliases NOT working inside bash shell script
# 8  
Old 12-13-2016
Can you source script2 from within script1?
# 9  
Old 12-13-2016
Hammer & Screwdriver
Quote:
Originally Posted by RudiC
Can you source script2 from within script1?
Yes, i did source in script1.sh as shown below.

Code:
more script1.sh
shopt -s expand_aliases; 
alias ln=ln_s 
echo "Starting Execution"
source  ~/script2.sh
~/script2.sh 
echo "End of Execution" 
ln_s()
{   
[[ -e $2 ]] && return   
ln -s "$1" "$2" 
}

But i get this error:

Code:
/opt/user1/script2.sh: line 1: ln_s: command not found

Why the error ?
# 10  
Old 12-13-2016
What is this:
Code:
source  ~/script2.sh
~/script2.sh

?
And, where do you define the function, and where do you call it?
# 11  
Old 12-13-2016
Quote:
Originally Posted by RudiC
What is this:
Code:
source  ~/script2.sh
~/script2.sh

?
And, where do you define the function, and where do you call it?
In Post# 9 i have shown that the function ln_s() is define in script1.sh.

I am sourcing script2.sh inside script1.sh here -> source ~/script2.sh and then i am executing script2.sh from within script1.sh here -> ~/script2.sh with the expectation that the ln command in script2.sh should be executed as ln_s thus calling the function.
Last edited by mohtashims; 12-13-2016 at 11:05 AM..
# 12  
Old 12-13-2016
Quote:
Originally Posted by mohtashims
In Post# 9 i have shown that the function ln_s() is define in script1.sh.
Yes, but unfortunately too late in the script.


Quote:
I am sourcing script2.sh inside script1.sh here -> source ~/script2.sh
OK, very good, the alias should be known, but not the function

Quote:
and then i am executing script2.sh from within script1.sh here -> ~/script2.sh
Why this second execution? And, neither alias nor function will be available

Quote:
with the expectation that the ln command in script2.sh should be executed as ln_s thus calling the function.
No, as explained.


Let me comment on your script snippet:

Code:
shopt -s expand_aliases;        # setting the necessary shell option
alias ln=ln_s                   # defining the alias IN THE CURRENT ENVIRONMENT in which the function IS NOT KNOWN YET
echo "Starting Execution" 
source  ~/script2.sh            # sourcing (=reading & executing) the script IN THE CURRENT ENVIRONMENT; alias known, function not known
~/script2.sh                    # running the script (again!) in a NEW subshell IN A NEW ENVIRONMENT; alias not known, function not known 
echo "End of Execution" 
ln_s()                          # defining the function for LATER USE!
{   
[[ -e $2 ]] && return   
ln -s "$1" "$2" 
}
.                               # from here on, ln will correctly call the function
.
.

I strongly recommend you get your head around shells and subshells, the difference between sourcing a collection of commands and executing them in a subshell, environment inheritance, and function definition.
This User Gave Thanks to RudiC For This Post:
mohtashims
# 13  
Old 12-14-2016
Quote:
Originally Posted by mohtashims
I have no write permissions on script2.sh ... i just have ownership of script1.sh.

Can you please suggest ?
Instead of an alias, you could maybe use an exported function:

Code:
ln() {   ln_s "$@" }
export -f ln
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