#subshell

[er-cryptid]

Subshells

-- 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

Patreon | Ko-fi

[ushf]

sudo internal or external to a loop?

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

sudo sh -c 'for name in Tunnel BatchMode; do 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

[music4thebasshead]

Exium - Subshell (Original Mix) [NHEOMA]

[sexweedandtechno]

Artist: Exium Track: Subshell --- Thanks for 600+ Subscribers!! I will post a set soon for your guys :)

[music4thebasshead]

Exium - Subshell (Pfirter Remix) [NHEOMA]

[ushf]

BASH shell level notes

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

http://stackoverflow.com/questions/59895/can-a-bash-script-tell-what-directory-its-stored-in https://codereview.chromium.org/15954011/ http://www.thefriendlycoder.com/2014/05/18/bash-error-handling/ http://bash.cyberciti.biz/guide/$0 http://www.xensoft.com/content/exploring-bashsource-array https://gist.github.com/mpdaugherty/2691574 http://stackoverflow.com/questions/4511407/how-do-i-know-if-im-running-a-nested-shell

[lapismoon]

私はお仕事でSolarisサーバの管理をするときにBourneシェルのスクリプトを よく作成するのですが、while (do～done)のブロック中に操作した変数の値が 変更されていない事象が発生して、頭を抱えていました。 その件についての議論をコピペします。