Shell Programmierung

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TranslationInfo:[Autor und Übersetzer]

original in en Katja and Guido Socher

en to de Katja Socher

AboutTheAuthor:[Eine kleine Biographie über den Autor]

Katja ist die deutsche Redakteurin von LinuxFocus. Sie mag Tux, Film & Fotografie und das Meer. Ihre Homepage findet sich hier.

Guido ist ein langjähriger Linuxfan und er mag Linux, weil es von ehrlichen und offenen Leuten entwickelt wurde. Dies ist einer der Gründe, warum wir es Open Source nennen. Seine Homepage ist auf linuxfocus.org/~guido.

Abstract:[Hier sollte eine kleine Zusammenfassung stehen]

ArticleIllustration:[Das Titelbild des Artikels]

ArticleBody:[Der eigentliche Artikel. Überschriften innerhalb des Artikels sollten h2 oder h3 sein.]

Warum Shell Programmierung?

Schreiben eines Skripts

    #!/bin/sh 
   

Kommentare

Variablen

varname=value

#!/bin/sh
# assign a value:
a="hello world"
# now print the content of "a":
echo "A is:"
echo $a

A is:
hello world

num=2
echo "this is the $numnd"

num=2
echo "this is the ${num}nd"

Shellbefehele und Steuerungsstrukturen

 cat file.txt | awk -F, '{print $1 "," $3 }' 

Adam Bor, 34, India
Kerry Miller, 22, USA

Adam Bor, India
Kerry Miller, USA

    grep "hello" file.txt | wc -l

find . -mtime -1 -type f -print

tar xvf file.tar infile1 infile2 ...

#!/bin/sh
# The ticks are backticks (`)  not normal quotes ('):
tar -zcvf lastmod.tar.gz `find . -mtime -1 -type f -print`

if ....; then
   ....
elif ....; then
   ....
else
   ....
fi

[ -f "somefile" ]  : Test if somefile is a file.
[ -x "/bin/ls" ]   : Test if /bin/ls exists and is executable.
[ -n "$var" ]      : Test if the variable $var contains something
[ "$a" = "$b" ]    : Test if the variables "$a" and  "$b" are equal

#!/bin/sh
if [ "$SHELL" = "/bin/bash" ]; then
  echo "your login shell is the bash (bourne again shell)"
else
  echo "your login shell is not bash but $SHELL"
fi

[ -f "/etc/shadow" ] && echo "This computer uses shadow passwors"

#!/bin/sh
mailfolder=/var/spool/mail/james
[ -r "$mailfolder" ] || { echo "Can not read $mailfolder" ; exit 1; }
echo "$mailfolder has mail from:"
grep "^From " $mailfolder

case ... in
...) do something here;;
esac

file lf.gz

ergibt:

lf.gz: gzip compressed data, deflated, original filename, 
last modified: Mon Aug 27 23:09:18 2001, os: Unix

#!/bin/sh
ftype=`file "$1"`
case "$ftype" in
"$1: Zip archive"*)
    unzip "$1" ;;
"$1: gzip compressed"*)
    gunzip "$1" ;;
"$1: bzip2 compressed"*)
    bunzip2 "$1" ;;
*) error "File $1 can not be uncompressed with smartzip";;
esac

select var in ... ; do
  break
done
.... now $var can be used ....

#!/bin/sh
echo "What is your favourite OS?"
select var in "Linux" "Gnu Hurd" "Free BSD" "Other"; do
        break
done
echo "You have selected $var"

What is your favourite OS?
1) Linux
2) Gnu Hurd
3) Free BSD
4) Other
#? 1
You have selected Linux

while ...; do
 ....
done

for var in ....; do
  ....
done

#!/bin/sh
for var in A B C ; do
  echo "var is $var"
done

#!/bin/sh
# list a content summary of a number of RPM packages
# USAGE: showrpm rpmfile1 rpmfile2 ...
# EXAMPLE: showrpm /cdrom/RedHat/RPMS/*.rpm
for rpmpackage in $*; do
  if [ -r "$rpmpackage" ];then
    echo "=============== $rpmpackage =============="
    rpm -qi -p $rpmpackage
  else
    echo "ERROR: cannot read file $rpmpackage"
  fi
done

#!/bin/sh
echo *.jpg

#!/bin/sh
echo "*.jpg"
echo '*.jpg'

#!/bin/sh
echo $SHELL
echo "$SHELL"
echo '$SHELL'

/bin/bash
/bin/bash
$SHELL

echo \*.jpg
echo \$SHELL

*.jpg
$SHELL

#!/bin/sh
# we have less than 3 arguments. Print the help text:
if [ $# -lt 3 ] ; then
cat <<HELP
ren -- renames a number of files using sed regular expressions

USAGE: ren 'regexp' 'replacement' files...

EXAMPLE: rename all *.HTM files in *.html:
  ren 'HTM$' 'html' *.HTM

HELP
  exit 0
fi
OLD="$1"
NEW="$2"
# The shift command removes one argument from the list of
# command line arguments.
shift
shift
# $* contains now all the files:
for file in $*; do
    if [ -f "$file" ] ; then
      newfile=`echo "$file" | sed "s/${OLD}/${NEW}/g"`
      if [ -f "$newfile" ]; then
        echo "ERROR: $newfile exists already"
      else
        echo "renaming $file to $newfile ..."
        mv "$file" "$newfile"
      fi
    fi
done

functionname()
{
 # inside the body $1 is the first argument given to the function
 # $2 the second ...
 body
}

#!/bin/sh
# vim: set sw=4 ts=4 et:

help()
{
    cat <<HELP
xtitlebar -- change the name of an xterm, gnome-terminal or kde konsole

USAGE: xtitlebar [-h] "string_for_titelbar"

OPTIONS: -h help text

EXAMPLE: xtitlebar "cvs"

HELP
    exit 0
}

# in case of error or if -h is given we call the function help:
[ -z "$1" ] && help
[ "$1" = "-h" ] && help

# send the escape sequence to change the xterm titelbar:
echo -e "\033]0;$1\007"
#

#!/bin/sh
help()
{
  cat <<HELP
This is a generic command line parser demo.
USAGE EXAMPLE: cmdparser -l hello -f -- -somefile1 somefile2
HELP
  exit 0
}

while [ -n "$1" ]; do
case $1 in
    -h) help;shift 1;; # function help is called
    -f) opt_f=1;shift 1;; # variable opt_f is set
    -l) opt_l=$2;shift 2;; # -l takes an argument -> shift by 2
    --) shift;break;; # end of options
    -*) echo "error: no such option $1. -h for help";exit 1;;
    *)  break;;
esac
done

echo "opt_f is $opt_f"
echo "opt_l is $opt_l"
echo "first arg is $1"
echo "2nd arg is $2"

cmdparser -l hello -f -- -somefile1 somefile2

opt_f is 1
opt_l is hello
first arg is -somefile1
2nd arg is somefile2

Search for -xx- in file f.txt:
grep -- -xx- f.txt

Beispiele

cp framework.sh myscript

#!/bin/sh
# vim: set sw=4 ts=4 et:
help()
{
  cat <<HELP
b2h -- convert binary to decimal

USAGE: b2h [-h] binarynum

OPTIONS: -h help text

EXAMPLE: b2h 111010
will return 58
HELP
  exit 0
}

error()
{
    # print an error and exit
    echo "$1"
    exit 1
}

lastchar()
{
    # return the last character of a string in $rval
    if [ -z "$1" ]; then
        # empty string
        rval=""
        return
    fi
    # wc puts some space behind the output this is why we need sed:
    numofchar=`echo -n "$1" | wc -c | sed 's/ //g' `
    # now cut out the last char
    rval=`echo -n "$1" | cut -b $numofchar`
}

chop()
{
    # remove the last character in string and return it in $rval
    if [ -z "$1" ]; then
        # empty string
        rval=""
        return
    fi
    # wc puts some space behind the output this is why we need sed:
    numofchar=`echo -n "$1" | wc -c | sed 's/ //g' `
    if [ "$numofchar" = "1" ]; then
        # only one char in string
        rval=""
        return
    fi
    numofcharminus1=`expr $numofchar "-" 1` 
    # now cut all but the last char:
    rval=`echo -n "$1" | cut -b 0-${numofcharminus1}`
}
    

while [ -n "$1" ]; do
case $1 in
    -h) help;shift 1;; # function help is called
    --) shift;break;; # end of options
    -*) error "error: no such option $1. -h for help";;
    *)  break;;
esac
done

# The main program
sum=0
weight=1
# one arg must be given:
[ -z "$1" ] && help
binnum="$1"
binnumorig="$1"

while [ -n "$binnum" ]; do
    lastchar "$binnum"
    if [ "$rval" = "1" ]; then
        sum=`expr "$weight" "+" "$sum"`
    fi
    # remove the last position in $binnum
    chop "$binnum"
    binnum="$rval"
    weight=`expr "$weight" "*" 2`
done

echo "binary $binnumorig is decimal $sum"
#

#!/bin/sh
# vim: set sw=4 ts=4 et: 
ver="0.1"
help()
{
    cat <<HELP
rotatefile -- rotate the file name 

USAGE: rotatefile [-h]  filename

OPTIONS: -h help text

EXAMPLE: rotatefile out
This will e.g rename out.2 to out.3, out.1 to out.2, out to out.1
and create an empty out-file

The max number is 10

version $ver
HELP
    exit 0
}

error()
{
    echo "$1"
    exit 1
}
while [ -n "$1" ]; do
case $1 in
    -h) help;shift 1;;
    --) break;;
    -*) echo "error: no such option $1. -h for help";exit 1;;
    *)  break;;
esac
done

# input check:
if [ -z "$1" ] ; then
 error "ERROR: you must specify a file, use -h for help" 
fi
filen="$1"
# rename any .1 , .2 etc file:
for n in  9 8 7 6 5 4 3 2 1; do
    if [ -f "$filen.$n" ]; then
        p=`expr $n + 1`
        echo "mv $filen.$n $filen.$p"
        mv $filen.$n $filen.$p
    fi
done
# rename the original file:
if [ -f "$filen" ]; then
    echo "mv $filen $filen.1"
    mv $filen $filen.1
fi
echo touch $filen
touch $filen

Fehlersuche

sh -x strangescript

sh -n your_script

Referenzen

• Die man page und die info page von bash sind sehr gut und du wirst dort noch viele weitere Tricks entdecken:
  man bash
  tkinfo bash
  (Ich hasse den Standardinfobrowser, aber tkinfo oder konqueror (der url ist info:/bash/Top ) sind ganz gut)
• Der LinuxFocus Artikel über GNU file utilities
• Der LinuxFocus Artikel über Reguläre Ausdrücke
• Der LinuxFocus Artikel über AWK
• Der LinuxFocus Artikel über Wichtige UNIX Befehle
• Wenn die bash auf deinem System nicht installiert ist oder du die neueste Version haben möchstest, kannst du sie von der GNU Webseite auf http://www.gnu.org herunterladen (um herauszufinden, ob bash schon auf deinem System installiert ist, tippe einfach bash. Wenn du keine Fehlermeldung bekommst, ist die bash schon installiert)