Running shell script inside shell script - good or bad?

Question

Recently i got an assignment at school, where we are to write a small program in Bash Scripting Language.

This shell script is supposed to accept some Positional Parameters or Arguments on the command line.

Now, with the help of an if-else statement i check if the argument is present, if the argument is present the script does what it is supposed to do, but if the argument is not present - i display an error message, prompting the user to input an argument and pass the argument again to the same shell script...

Now, i want to know if this approach is good or bad in Bash Programming paradigm. I'm slightly suspicious that this might run too many tasks in the background that are kept open or that are never ended and keep on consuming memory... please help.

Here's a small snippet (assume the script name to be script1.bash):

 #!/bin/bash

 if [ $# -gt 0 ]; then
      read -p "Please enter your name: " name
      script1.bash $name
 elif [ $# -eq 1 ]; then
      echo "Your name is $1!"
 fi

You should include the homework tag if this is a school assignment. — BMitch
– BMitch, Commented Mar 1, 2011 at 3:43
shell scripts running inside shell scripts? That's an abomination. — mob
– mob, Commented Mar 1, 2011 at 14:29

paxdiablo · Accepted Answer · 2011-03-01 03:37:59Z

4

It's ... questionable :-)

The main problem is that you're spawning a subshell everytime someone refuses to input their name.

You would be better of with something like:

#!/bin/bash
name=$1
while [[ -z "$name" ]] ; do
    read -p "Please enter your name: " name
done
echo "Your name is $name!"

which spawns no subshells.

answered Mar 1, 2011 at 3:37

paxdiablo

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4 Comments

Jasdeep Singh Over a year ago

thanks paxdiablo, i've tried doing some becnhmarking using top command, nothing shows up their... just wondering???

Jeremiah Willcock Over a year ago

Would his original code work if he used exec to do the recursive call?

paxdiablo Over a year ago

Well, his original code works as-is (other than the fact it should be $1 rather than $name in the elif bit) unless you hit ENTER so many times the system runs out of processes. exec would stop that from happening. My answer was more along the lines of only do what's needed. There's no point in starting another process (or even replacing the contents of the current process a la exec) when you can just whip up a while loop.

Jasdeep Singh Over a year ago

thanks for your input. I realized i goofed up in the second part of if-else statement. Thanks a lot!

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