To display some pre-formatted text onto screen, we need the following 2 capabilities:

Construct Multiple Text

There are 2 ways to construct multiple line strings:

• String literal

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  text = " First Line Second Line Third Line "

• Use cat

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  text = $(cat << EOF First Line Second Line Third Line EOF )

Print Multiple Text to Screen

For some reason, echo command will eat all the line break in the text, so we should use printf instead of echo.
And printf supports back-slash-escape, so we can use \n to print a new-line on screen.

As described in previous post, Mac OS launch its terminal as Log-In shell rather than Interactive Shell, which is different to default behavior of Unix and Linux. As a result, Terminal will load “bash_profile” as its profile rather than the normal “bashrc”.

This unique behavior might cause some problem when you try to port CLI tool from Unix or Linux.
Because basically, the ported app infers that the bash_profile should be loaded only once, and only when user just logged in. But in Mac OS, this inference is wrong, which can cause some weird problem.

This default behavior sometimes is annoying, and in fact, this Mac OS Terminal’s “unique” behavior can be configured. And even more, you can use other shell program, such as ksh, rather than the default bash.

Mac user can customize this behavior in Terminal’s Preferences dialog of Terminal app.

If you choose the command to launch bash, the launched shell will become a interactive shell, which will load .bashrc file rather than .bash_profile file.

In Linux and Unix world, there are 2 common used shell profiles: ~/.bashrc and ~/.bash_profile. These two profiles are usually used to initialize user bash environment, but there still are some slightly differences between them two.
According to bash manual, .bashrc is “interactive-shell startup file”, and .bash_profile is “login-shell startup file”.

What’s the difference between interactive-shell and login-shell

Basically, the login-shell means the shell opened when user log in via console. It could be the shell opened on local computer after you entered correct user name and password, or the shell opened when you ssh to a remote host.
So according to the bash_profile will be loaded only once, that’s right after you logged into a computer, either locally or remotely.

And, on the other hand, the interactive-shell could be more widely used, be seen more often. It is the shell opened after you logged in, such as the shell opened from KDE or Gnome.

Mac Terminal’s Pitfall

According to the manual, the Terminal App on Mac is the typical “interactive-shell”, so theoretically Terminal should load “.bashrc” to initialize the shell environment. But the fact is Terminal doesn’t load the “.bashrc”, instead it load “.bash_profile” for initialization.
So in a word, Mac’s Terminal doesn’t follow the routine strictly. We need to be aware it.

And not all the shell are interactive! If the shell is not interactive, the Terminal App won’t load the profile file to initialize the environment.
A typical non-interactive shell in the shell that TextMate used to run command script, which means in TextMate’s shell, these environment variables, path and even alias you used in you daily life might not be available for TextMate’s command.
And also the most hurt one, the rvm function also won’t be available in TextMate’s command shell, which means if you call rake or rails in TextMate’s command script, you are very possibly got error because it cannot find proper gem or other resources.
So you should always remember to source and run the “.bash_profile” file or setup these values once again.

Here is a bash script that acts as a TextMate command, which enables blogger to create new post without leaving TextMate.
It depends on “Post” task of the Rakefile in Jekyll Bootstrap.

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cd $TM_PROJECT_DIRECTORY
title=$(CocoaDialog standard-inputbox \
 --title "New Post" \
 --informative-text "Title of the new post:")
[[$(head -n1 <<<"$title") == "2" ]] && exit_discard
title=$(tail -n1 <<<"$title")
output=$(rake post title="$title")
expr="^\(in (.*)\) Creating new post: (.*)$"
if [[$output =~ $expr ]]; then
   	project=${BASH_REMATCH[1]}
	post=${BASH_REMATCH[2]}
	echo "new post file created at $post"
	exit_show_tool_tip
else
   	echo "Error"
	exit_show_tool_tip
fi

This is a script to populate computer hardware configuration in Linux.

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#!/bin/bash
# CPU
cat /proc/cpuinfo |  grep -e "model name" -e "cores" -m 2 && cat /proc/cpuinfo | grep -e "physical id"| sort  | uniq -c
# Memory
free -got
# Disk
df -lh -t ext4 --total

The most common task when operating the servers is to distribute a file to multiple servers.
So I wrote a piece of shell script to solve this problem:

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#!/bin/bash  
echo "mscp <source file> <target dir>"  
SourceFile=$1  
TargetDir=$2  
echo "Copy $SourceFile to $TargetDir as $RemoteUser"  
echo "Enter the servers:"  
if [-f $SourceFile ]  
then  
  printf "File found, preparing to transfer\n"  
  while read server  
  do  
  scp -p $SourceFile ${server}:$TargetDir  
  done  
else  
  printf "File \"$SourceFile\"not found\n"  
  exit 1  
fi  
exit 0

call the script mscp <source file> <target dir>, then the script will ask you the list of target servers. So you can type them one by one. If the remote user is different than you current user, you can also explicitly identify it by typeing user@server

Beside the previous scenario, there is a more common sceanrio, that you have got a server list stored in afile already. Then instead of type the servers line by line, you can pipe the file content to the script.
e.g:

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cat server_list.txt > mscp src_files dest_path