#subshell

-- indicated by the letter

-- specifies the orbital’s shape

-- possible letters      -- s      -- p      -- d      -- f

-- each letter corresponds to a different shape

-- orbitals within the s subshell have a spherical shape

-- this is a three-dimensional probability map      -- represented with dots      -- dot density is proportional to the probability of finding the electron

Supposing: some set of files or other resources only accessible with temporarily elevated privileges obtained through sudo. How should a loop to iterate over them call the sudo command? There are two options: shove it inside the for loop or call the whole for loop from within a shell with elevated privs.

In this specific case I wanted to verify that a fresh RPM package had made the changes it claimed it had made.

Within the loop

This works fine for cases where there are only a few items to iterate through. If there are many, then it is necessary to start looking at the timeout values set for sudo.

for name in Tunnel BatchMode; do sudo grep -r $name /etc/ssh/; done

[sudo] password for ushf: /etc/ssh/sshd_config.rpmnew:#PermitTunnel no /etc/ssh/sshd_config:#PermitTunnel no /etc/ssh/ssh_config:# Tunnel no /etc/ssh/ssh_config:# TunnelDevice any:any /etc/ssh/ssh_config:# BatchMode no

Shove the whole thing into a shell

Take a look at the older Aileen Frisch UNIX Power Tools. It has a section (7.9) which says that in the "top level shell" for BASH and tcsh the environment variable SHLVL takes on the following values: 1 == toplevel, 2 == next subshell, etc.

A later section (38.4) says that each shell script runs in a subshell unless you use the source or . commands to start the shell script. In these latter cases the script is read into the current shell instead of spawning a subshell. Sourced shell scripts can only contain commands which could be typed in at the commandline. They cannot read in binaries.

As usual, once I have read enough to know what to look for there is a good answer on stackoverflow

Links on finding where we are with Bash