Guillaume: /* Manipulating variables */

2010-03-30T08:58:41Z

‎Manipulating variables

Guillaume: 1 revision

2008-12-03T10:26:56Z

1 revision

193.136.136.173: /* While */

2008-08-01T12:42:03Z

‎While

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==Configuring your environment variables: .bashrc==

> vim ~/.bashrc
# .bashrc

# Source global definitions
if [ -f /etc/bashrc ]; then
. /etc/bashrc
fi

# User specific aliases and functions
export PATH=\
./bin:\
/opt/local/bin:\
/opt/local/gnu/bin:\
/opt/local/gnome2/bin:\
/opt/local/gnome1/bin:\
/opt/local/mozilla/bin:\
/usr/local/netcdf/include:\
/usr/local/netcdf/lib:\
/usr/local/netcdf/bin:\
$PATH

export MANPATH=\
/opt/local/man:\
/opt/local/gnu/man:\
/opt/local/gnome2/man:\
/opt/local/gnome1/man:\
/opt/local/mozilla/man:\
$MANPATH

==Flow control==
===While===
Count=0
while test $Count -lt 10
do
echo "Inside first loop $Count"
Count=`expr $Count + 1`
done
echo "Outside first loop $Count"

===If===
if [ $# -ne "$ARGS" ]; then
echo "Description: Creates ring of tw bots"
echo "Usage: > `basename $0` tw_ringof.txt"
exit $E_BADARGS
fi

===Case===
case "$3" in
'test')
twitbot="pointptteste:pointpt"
;;
*)
twitbot="weather${city}:weather"
;;
esac

==Examples==

===Find string in files===
Using the [[Find]] is good under windows when one whishes to search for a string inside a set of files. But in linux one must rely on alternative routes. This example uses '''for''', '''pipes''', '''grep''' and '''cat''' and prints out any line matching <code>MATCH</code> from a list of files containing the <code>FILEPATTERN</code> pattern:
> for i in `find . | grep 'FILEPATTERN'`; do cat $i | grep MATCH;done
Now, if you want to change the <code>MATCH</code> pattern with a <code>SUBST</code> pattern, then check out [[Sed]].

===Replicate directories tree===
In order to duplicate the directory tree simply type in bash inside the root of the directory to duplicate:
> for i in `find . | grep '[^.]....$' | grep '[^.]...$' | grep '[^.]..$'`; do mkdir NEWROOT/$i; done
where ''NEWROOT'' is the new home directory of the duplicated directory tree.

Here's a more elegant way of doing the directory skeleton replication:
> for i in `find ROOT -type d | sed 's/ROOT/NEWROOT/g'`; do mkdir $i; done

Now you are able to transfer files between the original directory tree and the duplicated directory tree. You can transfer them one file at a time, or by extensions:
> for i in `find . | grep '\.SUFF$'`; do cp
where ''SUFF'' is the file extension. (Remember to execute the command from within the original directory tree's root.)

===[[Piping]] output===
Here's one example that pipes the output of a program to the input of another program
> echo My Sister | (read a b; echo $a; echo$b)
My
Sister

Here's one example to mute the stdout and the stderr
> echo coucou >/dev/null 2>&1

===Using if===
> if [ `diff ${file}.txt ${file}.tmp | wc -l` -gt 0 ]; then echo Ok; fi

===Reading and setting environment variables===
This examples creates the environment variable '''$mess''' by reading the line from file.txt:
> read mess < file.txt

===Manipulating variables===
> ${var/pattern/replacement}

> let var = $othervar + 3

==External References==
*[http://www.faqs.org/docs/bashman/bashref.html bash reference manual].

[[Category:linux]]
[[Category:Script]]

← Older revision		Revision as of 08:58, 30 March 2010
Line 96:		Line 96:

	> let var = $othervar + 3		> let var = $othervar + 3
		+
		+	> ${var:3:2}
		+	substring from 3-rd + 1 char with an offset of 2 char.
		+
		+	> ${#var}
		+	returns the number of chars in $var
		+
		+	> ${var:0:${#var}-3}
		+	substring everything except the last 3 chars
		+
		+	> ${var:-3}
		+	substring only the last 3 chars

	==External References==		==External References==

← Older revision	Revision as of 10:26, 3 December 2008
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Guillaume: /* Manipulating variables */

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193.136.136.173: /* While */