Linux tricks I learned today

I learned some Linux related tricks today:
1 Tutorial: Conditions in bash scripting (if statements)
This tutorial probably is one of the best and thorough explanation of IF conditions syntaxes I can find so far.

2 Tutorial: The best tips & tricks for bash, explained

3 Manipulating Strings
I was looking for ways to replace strings in a bash script, and found out this article is really helpful.

Substring Replacement

${string/substring/replacement}

Replace first match of $substring with $replacement.

${string//substring/replacement}

Replace all matches of $substring with $replacement.

1 stringZ=abcABC123ABCabc 2  3 echo ${stringZ/abc/xyz} # xyzABC123ABCabc 4  # Replaces first match of 'abc' with 'xyz'. 5  6 echo ${stringZ//abc/xyz} # xyzABC123ABCxyz 7  # Replaces all matches of 'abc' with # 'xyz'.

${string/#substring/replacement}

If $substring matches front end of $string, substitute $replacement for $substring.

${string/%substring/replacement}

If $substring matches back end of $string, substitute $replacement for $substring.

1 stringZ=abcABC123ABCabc 2  3 echo ${stringZ/#abc/XYZ} # XYZABC123ABCabc 4  # Replaces front-end match of 'abc' with 'XYZ'. 5  6 echo ${stringZ/%abc/XYZ} # abcABC123ABCXYZ 7  # Replaces back-end match of 'abc' with 'XYZ'.

4 Advanced Bash-Scripting Guide

5 Highlight all search pattern matches
To turn off search pattern matches highlight, do ":set hls!" in vi command mode.

6 Turn on or off color syntax highlighting in vi or vim\

7 Arithmetic Expressions in BASH
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In bash version 3.2 and later you can (and should) use $(( )) or let for integer arithmetic expressions. The idea of ((...)) construct is similar to [[...]] construct introduced in ksh88 -- provide built in capabilities for arithmetic instead of calling external functions. The (( ))compound command evaluates an arithmetic expression and sets the exit status to 1 if the expression evaluates to 0, or to 0 if the expression evaluates to a non-zero value.  All arithmetical operations are performed  on integers. For example:

 i=$(( i + 1 ))
 let i+=1

or

 i=$(( i++))
 let i++

You must not have spaces around the equals sign, as with any bash variable assignment.
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8 Bash For Loop Examples
   Three-expression bash for loops syntax
   Conditional exit with break

   Early continuation with continue statement

9 Best of Vim Tips