Bash - Revision history

Christoph: /* Christoph's Additions */

2023-05-09T19:04:58Z

‎Christoph's Additions

2023-04-19T23:01:17Z

‎shopt

2022-04-18T16:06:10Z

‎More Special Keybindings

2017-05-11T01:45:12Z

‎Integer mathematics

2017-05-08T19:17:37Z

‎Tests

2017-05-08T19:16:29Z

‎In-process regular expressions

2017-05-08T19:15:20Z

‎EOF

2015-03-01T18:57:26Z

‎I/O redirection

2015-02-24T02:44:32Z

‎Other guides and tutorials

2015-02-24T01:19:52Z

‎Variables

← Older revision		Revision as of 19:04, 9 May 2023
Line 625:		Line 625:

	[christoph@christophchamp]:/home/christoph>		[christoph@christophchamp]:/home/christoph>
		+	</pre>
		+
		+	<pre>
		+	$ echo $BASH_VERSION
		+	4.4.20(1)-release
		+
		+	$ echo $BASH_VERSION[0]
		+	4.4.20(1)-release[0]
		+
		+	$ echo $OSTYPE
		+	linux-gnu
	</pre>		</pre>

@@ Line 561: / Line 561: @@
 ; sourcepath : the source (.) builtin uses the value of PATH to find the directory containing the file supplied as an argument.
 ; xpg_echo : the echo builtin expands backslash-escape sequences by default.
 ==Bash (Shellshock) vulnerability==

@@ Line 116: / Line 116: @@
 </div>
 <br clear="all"/>
 === More Special Keybindings ===
@@ Line 147: / Line 153: @@
 </div>
 <br clear="all"/>
 ===Bash Bang (!) commands===

@@ Line 180: / Line 180: @@
 The <tt>((...))</tt> command can also be used in conditional statements, because its [[exit status]] is 0 or 1 depending on whether the condition is true or false:
-  if ((VAR == Y * 3 + X * 2))
+  if ((VAR == Y * 3 + X * 2)); then
- then
+   echo Yes
-         echo Yes
   fi

@@ Line 413: / Line 413: @@
 *<code>!expr</code> = True if the expr evaluates to false.
 *<code>expr1 -a expr2</code> = True if both expr1 and expr2 are true.
-*<code>expr1 -o expr2</code> = True is either expr1 or expr2 is true.
+*<code>expr1 -o expr2</code> = True if either expr1 or expr2 is true.
 The syntax is:

@@ Line 281: / Line 281: @@
 The regular expression syntax is the same as that documented by the regex(3) [[man page]].  The exit status of the above command is 0 if the regex matches the string, 1 if it does not match.  Parenthesized subexpressions in the regular expression can be accessed using the shell variable <tt>BASH_REMATCH</tt>, as follows:
-  if <nowiki>[[ abcfoobarbletch =~ 'foo(bar)bl(.*)' ]]</nowiki>
+  if <nowiki>[[ abcfoobarbletch =~ 'foo(bar)bl(.*)' ]]</nowiki>; then
- then
+   echo The regex matches!
-         echo The regex matches!
+   echo $BASH_REMATCH      -- outputs: foobarbletch
-         echo $BASH_REMATCH      -- outputs: foobarbletch
+   echo ${BASH_REMATCH[1]} -- outputs: bar
-         echo ${BASH_REMATCH[1]} -- outputs: bar
+   echo ${BASH_REMATCH[2]} -- outputs: etch
-         echo ${BASH_REMATCH[2]} -- outputs: etch
   fi

@@ Line 237: / Line 237: @@
 ====EOF====
-The <code>`cat <<EOF`<code> Bash syntax is very useful when one needs to work with multi-line strings in Bash (e.g., when passing a multi-line string to a variable, file, or a piped command).
+The <code>`cat <<EOF`</code> Bash syntax is very useful when one needs to work with multi-line strings in Bash (e.g., when passing a multi-line string to a variable, file, or a piped command).
 * Pass a multiline string to a variable:

@@ Line 235: / Line 235: @@
    # search for filenames which end with the letter "h"
    VAR=$(find . -name "*h")
 ===In-process regular expressions===

@@ Line 570: / Line 570: @@
 *[http://deadman.org/bash.html Advancing in the Bash Shell tutorial]
 *[http://www.vias.org/linux-knowhow/bbg_intro_10.html Linux Know-How] including the Bash Guide for Beginners
-*[http://www.bashscripts.org/ BashScripts.org]
+*[http://www.bashscripts.org/ BashScripts.org]<!--
 *[http://www-128.ibm.com/developerworks/library/l-bash.html Bash by example - Part 1]
 *[http://www.ibm.com/developerworks/library/l-bash2.html Bash by example - Part 2]
-*[http://www.ibm.com/developerworks/library/l-bash3.html Bash by example - Part 3]
+*[http://www.ibm.com/developerworks/library/l-bash3.html Bash by example - Part 3]-->
 *[http://www.faqs.org/docs/linux_intro/x7003.html Common features]
 *[http://www-128.ibm.com/developerworks/aix/library/au-satbash.html?ca=dgr-lnxw97bash Get the most out of bash]
 ===Custom .bashrc or .bash_profile===
 *[http://static.askapache.com/askapache-bash-profile.txt askapache-bash-profile.txt]
 [[Category:Scripting languages]]

← Older revision		Revision as of 01:19, 24 February 2015
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	The "shift" command can be used to shift command line arguments to the left, i.e., <code>$1</code> becomes the value of <code>$2</code>, <code>$3 </code>shifts into <code>$2</code>, etc. The command, "shift 2" will shift 2 places meaning the new value of <code>$1</code> will be the old value of <code>$3</code> and so forth.		The "shift" command can be used to shift command line arguments to the left, i.e., <code>$1</code> becomes the value of <code>$2</code>, <code>$3 </code>shifts into <code>$2</code>, etc. The command, "shift 2" will shift 2 places meaning the new value of <code>$1</code> will be the old value of <code>$3</code> and so forth.
		+
		+	* Print specific characters stored in a variable:
		+	# The syntax is ${variable:start:length}. Omitting "length" value gives rest of string.
		+	$ val="hello"
		+	$ echo ${val:0:1} # Print out the first character of $val ("h" in this example)

	===Tests===		===Tests===