Issues while trying to run a shell script using the command sh <filename.prog>

Shell Programming and Scripting
1

Hi,

I'm facing issues while trying to run a sample program on Linux.
If I try to run the script using the command "sh <filename.prog>", it doesn't work. But, if I try to execute it using the command "ksh <filename.prog>", it works fine.

Even ". ./filename.prog" works fine.

Can you please help in fixing this and make the file execute using the command "sh <filename.prog>".

Code:

#!/bin/sh
  
 printf "%s\n" "set pages 0 serverout on feed off" \
          "SELECT sysdate from dual;" \
           |sqlplus -s username/password \
           |{ read var1; }
echo "date is " $var1
2

Use code tags for code please, the button.

This particular script will only work in ksh because of the way its constructed. It puts read after a pipe, which is something you can do in ksh but not a vanilla bourne shell because of the opposite order they create subshells.

You could use $( ) braces instead of read here, which ought to work in both:

DATE=$(printf "%s\n" "set pages 0 serverout on feed off" \
          "SELECT sysdate from dual;" \
           |sqlplus -s username/password )
echo "date is $DATE"
1 Like
3

Thanks for your response Corona. We have a similar code in almost 70+ programs and it would be a little tough to change it every where. Would it be a good idea to make the "sh" present under "/bin" to point to "ksh" i.e. creating a soft link for sh to point to ksh and try running it?

4

I'd be wary of doing that. The difference you've just shown can as easily break programs as fix them, changing it globally could have wider problems, and #!/bin/sh is used by all sorts of system things.

Might it be easier to change the #!/bin/sh part to #!/bin/ksh in those 70+ programs?

5

I tried changing the first line from #!/bin/sh to #!/bin/ksh, but it didn't work.
It still doesn't work when I try to execute the script as "sh <filename.prog>"

6

That's because by running 'sh programname' you're asking sh to run that file. The #!/bin/ksh line only gets used when you do ./file.sh.

If they have to work in plain sh, you'll have to update them, they were definitely written for ksh.

2 Likes
7

Thank you Corona.

1 Like