Unix man

Where does the Unix man command look for documents?

Start by running

/usr/libexec/path_helper -s

That shows a standard MANPATH value

/usr/share/man:/usr/local/share/man:/usr/X11/man

If you have man pages in other locations, just add them to the end of MANPATH, using standard *nix syntax.

Unix/Linux run levels

See Wikipedia entry.

Standard Unix/Linux run levels

Unix / Mac / DOS / Windows Line Termination

LF = ’0x0A’  o’012′  ‘\n’
CR = ’0x0D’  o’015′  ‘\r’

Unix, Linux – LF
MAC – LF
Windows – CR LF

REMEMBER!!!!

FTP on raw text files CONVERTS LINE TERMINATION between platforms. Doesn’t if text files are zipped.

Crontab format

See Wikipedia

# +---------------- minute (0 - 59)
# |  +------------- hour (0 - 23)
# |  |  +---------- day of month (1 - 31)
# |  |  |  +------- month (1 - 12)
# |  |  |  |  +---- day of week (0 - 6) (Sunday=0 or 7)
# |  |  |  |  |
  *  *  *  *  *  command to be executed

How a bash shell starts up under Unix and Linux

How a bash shell starts up under Unix and Linux

Interactive, login shell

Roughly speaking, an interactive login shell is what is invoked when you open up a new terminal window.

In order, the following files are loaded

/etc/profile
And first one found of ~/.bash_profile,  ~/.bash_login, ~/.profile

At exit,

~/.bash_logout

Interactive, non-login shell

Roughly speaking, an interactive, non-login shell is what you get when you type ‘bash’ or ‘su’ at the command prompt, or a file has something similar to ‘#!/bin/bash’ at the top.

An interactive, non-login shell inherits the parent shell environment.

In order, the following files are loaded

~/.bashrc

Remote shell and remote shell commands

A remote shell is one started up by rshd or ssh where you then interact at the prompt. The normal rules for an interactive, login shell apply.

In order, the following files are loaded

~/.bashrc

A remote shell command is a command similar to:

ssh me@10.1.10.123 "ls"

A remote shell command does not inherit any environment.

In order, the following files are loaded

~/.bashrc

/etc/bashrc

/etc/bashrc is not a standard part of the bash startup sequence. However, by convention, most bash distributions include something similar to

if [ -f /etc/bashrc ]; then
. /etc/bashrc
fi

either in /etc/profile or in ~/.bashrc. This loads the content of /etc/bashrc.

What do you include where?

Conventional advice says:

• Environment settings go in /etc/profile (global) or ~/.bash_profile,  ~/.bash_login, ~/.profile (local)
• Functions, aliases etc. go in /etc/bashrc or ~/.bashrc

As far as this goes, I agree, but it’s not complete. This incompleteness is the main reason for this note.  Remember

• Remote shell commands do not inherit any of the custom environment settings (no parent shell!)

So, if you want a standalone ‘ssh’ command to function correctly, and see all your custom PATH settings and other environment settings, you need to ensure the environment is loaded.

What I’ve done is to bracket my environment settings in a conditional statement, and invoke them from ~/.bashrc.

# My environment file - e.g. ~/.bash_profile
if [[ ${my_environment_loaded:-false} == false ]]
then
... (set your environment here)
    my_environment_loaded=true
fi

and in ~/.bashrc, modify the standard format

if [ -f /etc/bashrc ]; then
        . /etc/bashrc
fi

to something similar to

if [ -f /etc/bashrc ]; then
        . /etc/bashrc
        .  ~/.bash_profile
fi