Script calling hierarchy

Shell Programming and Scripting
1

If a.sh calls b.sh, how can we know inside b.sh that it was called by a.sh?

2

The variable $PPID contains the PID of the parent process. You need to parse the output of ps (or know how to fish it out of the /proc file system if your OS has that) to find the name of the command of that PID.

3

As long as this isn't for security reasons, finding out the name isn't so tough. Check your ps command, which might contain the option to spit out the command name of a given pid. For instance, on Linux, I can do this:

ps --no-header -o cmd $PPID

4

Thanks both of you who've replied. I've successfully verified its utility. See below:

[root@IMITS174 perl_scripts]# cat a.sh
#!/bin/sh

sh b.sh
[root@IMITS174 perl_scripts]#
[root@IMITS174 perl_scripts]#
[root@IMITS174 perl_scripts]# cat b.sh
#!/bin/sh

echo "I am b"
parent_name=`ps --no-header -o ucmd $PPID`
echo "Parent PID is $PPID"
echo "Parent is $parent_name"
[root@IMITS174 perl_scripts]#
[root@IMITS174 perl_scripts]# ./a.sh
I am b
Parent PID is 18251
Parent is a.sh
[root@IMITS174 perl_scripts]#
[root@IMITS174 perl_scripts]#
[root@IMITS174 perl_scripts]# ./b.sh
I am b
Parent PID is 2014
Parent is bash

Note however: I've changed "cmd" to "ucmd" to make sure I don't get the annoying "/bin/sh" prefix to the calling program a.sh.

Thanks once again! Hope the above snippet helps anyone who wants to use it.

5

By the way, what would you do in case of Windows? Assume instead of .sh, you are dealing with .pl....?