=====BASH=====

Weiterführende [[BashLinks Links]]
Seite zum Thema [[LinuxStreamProcessing Streamverarbeitung]] 


==a==Standard-IO, Error-IO, File-IO und Pipes==a==

||A||Befehl ausführen und auf Beendigung warten ||
||A & ||  Befehl im Hintergrund ausführen||
||A ; B ||Befehl A ausführen, dann Befehl B||
||(A; B)||Befehle als Gruppe in einer Shell ausgeführt||
||A ""|"" B || Pipe; Die Ausgabe von A wird an B als Eingabe weitergeleitet||
||A $(B) || Die Ausgabe von B wird zu Befehlsargumenten von A||
||A && B || B wird ausgeführt, wenn A ohne Fehler ausgeführt wurde||
||A ""||"" B||  B wird ausgeführt, wenn bei A ein Fehler aufgetreten ist||
||A > out.txt|| Die Ausgabe (Fehlermeldungen ausgenommen) von A in die Datei out.txt schreiben; Die Datei wird überschrieben||
||A "">>"" out.txt|| Die Ausgabe (Fehlermeldungen ausgenommen) von A an den Inhalt der Datei out.txt anhängen||
||A 2> out.txt|| Die Fehlermeldungen von A an in die Datei out.txt schr iben||
||A < in.txt|| Der Inhalt von in.txt wird als Eingabe an A weitergeleitet||




==a==for-Schleife==a==

Ergebnisse eines Ausdrucks, in dem Fall //ls// in einer Schleife bearbeiten in dem Fall Ausgabe mit //echo//
%%(bash)
for i in * ; do echo "Datei: $i" ; done
%%

Alternative
%%(bash)
for i in `ls` ; do echo "Datei: $i" ; done
%%

Als Skript
%%(bash)
#!/bin/bash
for dot in `ls *.dot`
do
  echo $dot
  dot -Tpng $dot -o $dot.png 
done
%%

Zählen
%%(bash)
for (( i=4; i<20; i++ )); do echo $i ; done
%%


==a==While==a==

%%(bash)
 while [ condition ]
		   do
		   [Kommandos]
		   done
%%

Endless loop
%%(bash)
while [ true ]
do
	...
done
%%

==a==Variablen==a==

Zahl inkrementieren
%%(bash)
I=1
expr $I + 1
%%

Besser
%%
zahl=1
zahl=$(( $zahl + 1 ))
%%


String zuweisen
%%
set A=Dies ist ein Test
echo %A%
set B=%A%
echo %B%
%%

Pfad hinzufügen
%%
set PATH=%PATH%;C:\rnsget
%%

Set alle Variablen auflisten
%%
set 
%%

==a==Vordefinierte Variablen==a==

$0 ist der Skript-Aufruf; z.B. ./scripts/script.sh
$1 ist der erste Übergabeparameter an das Skript
$2 ist der zweite Übergabeparameter
usw.


==a==Tricks==a==

In den Skript-Pfad wechseln
%%(bash)
#Change to script directory
cd `dirname $0`
%%

%%(bash)
#Print working directory full path again
pwd
%%

basename 
%%(bash)
# Output working directory name (short)
basename `pwd`
#Strip non-directory suffix from the script name
dirname $0
%%

Merke altes Verzeichnis
%%(bash)
OLDDIR=`pwd`     #Save current dir
cd `dirname $0`  #Change to script directory or any other directory
# do something else
cd $OLDDIR       #Change back to old dir
%%


==a==Variablen-Tests==a==

=a=Zahlenvergleich mit anschließender Programmverzweigung=a=
%%(bash)
VALUE=5
test $VALUE -gt 4 && echo "Größer als 4" || echo "Kleiner oder gleich 4"
%%

=a=Vergleich=a=
%%(bash)
[ "abc" != "xyz" ] ; echo $?
%%

=a=String is not null=a=
%%(bash)
test -n "$DISPLAY" ; echo $?
test -n "$DISPLAY" && echo "OK"
%%

Mit IF
%%(bash)
if [ "$a" -gt "0" ]; then
			   echo 'true'
else
			   echo 'false'
fi
%%

=a=Integer comparison=a=
%%(bash)
	-eq is equal to 
		if [ "$a" -eq "$b" ]
	-ne is not equal to
		if [ "$a" -ne "$b" ]
	-gt is greater than
		if [ "$a" -gt "$b" ]
	-ge is greater than or equal to
		if [ "$a" -ge "$b" ]
	-lt is less than
		if [ "$a" -lt "$b" ]
	-le is less than or equal to
		if [ "$a" -le "$b" ]
	<   is less than (within double parentheses)
		(("$a" < "$b"))
	<=  is less than or equal to (within double parentheses)
		(("$a" <= "$b"))    
	>   is greater than (within double parentheses)
		(("$a" > "$b"))
	>=  is greater than or equal to (within double parentheses)
		(("$a" >= "$b"))


%%

=a=String comparison=a=
%%(bash)
	=   is equal to
		if [ "$a" = "$b" ]
	==  is equal to
		if [ "$a" == "$b" ]
	!=  is not equal to
		if [ "$a" != "$b" ]
		This operator uses pattern matching within a [[ ... ]] construct.
	<   is less than, in ASCII alphabetical order
		if [[ "$a" < "$b" ]]
		if [ "$a" < "$b" ]
		Note that the "<" needs to be escaped within a [ ] construct.
	>   is greater than, in ASCII alphabetical order
		if [[ "$a" > "$b" ]]
		if [ "$a" > "$b" ]
		Note that the ">" needs to be escaped within a [ ] construct.
		See Example 26-11 for an application of this comparison operator.
	-z  string is "null", that is, has zero length
	-n  string is not "null".
	
	
%%

=a=Compound comparison=a=
%%(bash)

	-a  logical and
		exp1 -a exp2 returns true if both exp1 and exp2 are true.
	-o  logical or
		exp1 -o exp2 returns true if either exp1 or exp2 are true.
		
		
%%

=a=Multiple conditions=a=
%%(bash)    
	Using the [[ ... ]] test construct, rather than [ ... ] can prevent many logic 
	errors in scripts. For example,the &&, ||, <, and > operators work within 
	a [[ ]] test, despite giving an error within a [ ] construct.

	Example:
	[[ $umlA -le $umlN && -n $umlN ]]


%%




==a==File tests==a==
%%(bash)
	-e  file exists
	-a  file exists
		This is identical in effect to -e. It has been "deprecated," and its use is discouraged.
	-f  file is a regular file (not a directory or device file)
	-s  file is not zero size
	-d  file is a directory
	-b  file is a block device (floppy, cdrom, etc.)
	-c  file is a character device (keyboard, modem, sound card, etc.)
	-p  file is a pipe
	-h  file is a symbolic link
	-L  file is a symbolic link
	-S  file is a socket
	-t  file (descriptor) is associated with a terminal device
		This test option may be used to check whether the stdin ([ -t 0 ]) or stdout ([ -t 1 ]) in
		a given script is a terminal.
	-r  file has read permission (for the user running the test)
	-w  file has write permission (for the user running the test)
	-x  file has execute permission (for the user running the test)
	-g  set-group-id (sgid) flag set on file or directory
		If a directory has the sgid flag set, then a file created within that directory belongs to the group that
		owns the directory, not necessarily to the group of the user who created the file. This may be useful
		for a directory shared by a workgroup.
	-u  set-user-id (suid) flag set on file
	-k  sticky bit set
	-O  you are owner of file
	-G  group-id of file same as yours
	-N  file modified since it was last read
	-nt f1 -nt f2
		file f1 is newer than f2
	-ot f1 -ot f2
		file f1 is older than f2
	-ef f1 -ef f2
		files f1 and f2 are hard links to the same file
	!   "not" -- reverses the sense of the tests above (returns true if condition absent).

%%

==a==Parallel processing in BASH==a==

http://stackoverflow.com/questions/13296863/difference-between-wait-and-sleep

%%(bash)
sleep 10 &
wait 
%%


==a==BASH error handling==a==

Exit status
%%$?%%

%%(bash)
#!/bin/bash
echo "Test with unknown command should fail."
foofoo 2> /dev/null
exitcode=$?
echo $exitcode
if [ $exitcode -ne 0 ]; then
	echo "Error"
else
	echo "OK"
fi

echo " "

echo "Test with successfull executed command should return 0."
ls > /dev/null
exitcode=$?
echo $exitcode
if [ $exitcode -ne 0 ]; then
	echo "Error"
else
	echo "OK"
fi
%%


Result
%%
Test with unknown command should fail.
127
Error

Test with successfull executed command should return 0.
0
OK
%%

==a==Create enumerated files and directories==a==

%%(bash)
mkdir dir{0..9}
%%

dir0
dir1
dir2
...
dir9

==a==Console colors==a==

[[PythonBashConsoleColor Bash color output in Python]]



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Siehe auch {{backlinks}}