Bash Samples

Find a particular class file in a directory of jar files

 
#!/bin/sh
findclass='ClassFileName'
for f in `ls`
do
  jar tvf $f | grep ${findclass}
  if [ $? = '0' ]
  then
    echo "Found ${findclass} in $f file."
  fi
done
 

Find a particular class file in all jar files

 
#!/bin/sh
findclass='ClassFileName'
for f in `find . -name "*.jar"`
do
  jar tvf $f | grep ${findclass}
  if [ $? = '0' ]
  then
    echo "Found ${findclass} in $f file."
  fi
done
 

Use getopts

 
#--------------------------------------------
# Get options
#--------------------------------------------
while getopts ":a:b:r:" opt
do
  case $opt in
    a)
      alpha=$OPTARG
      ;;
    b)
      beta=$OPTARG
      ;;
    r)
      gamma=$OPTARG
      ;;
    \?)
      echo "Invalid option: -$OPTARG"
      ;;
    :)
      echo "Option -$OPTARG requires an argument."
      ;;
  esac
done
 

grep Examples

 
# grep one of multiple strings
grep "string1\|string2\|string3"
 
# Inverse grep
grep -v "notThisString"
 

Remove Old Log Files

 
# List log files older than 30 days
find . -type f -mtime +30 -type f -name "*.log" -exec ls -altr {} \;
 
# Remove log files older than 30 days
find . -type f -mtime +30 -type f -name "*.log" -exec rm {} \;
 
# Remove log files older than 3 days
find . -type f -mtime +3 -type f -name "*.log" -exec rm {} \;
 

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Bash Array

Assign Array Elements

 
# Assign array elements
echo
myArr[0]='one'
myArr[1]='two'
myArr[10]='ten'
# Access array elements. *Curly brackets* are important.
echo "\${myArr[0]}: ${myArr[0]}"  # ${myArr[0]}: one.
# Echo all elements
echo "\${myArr[@]}: ${myArr[@]}" # ${myArr[@]}: one two ten
 
# Initialize array
echo
myArr3=( one two three four )
# Echo all elements
echo "\$myArr3[@]: ${myArr3[@]}" # $myArr3[@]: one two three four
# Number of array elements
echo "\$#myArr3[@]: ${#myArr3[@]}" # $#myArr3[@]: 4
 
# Initialize array
echo
myStr2='one two three four'
myArr2=( $myStr2 )
# Echo all elements
echo "\${myArr2[@]}: ${myArr2[@]}" # ${myArr2[@]}: one two three four
 

Tokenize String Into Array

 
myString2=one:two::four
oldIFS=$IFS
IFS=:
myArr2=( $myString2 )
IFS=$oldIFS
echo ${myArr2[0]}  # Output: 'one'
echo ${myArr2[1]}  # Output: 'two'
echo ${myArr2[2]}  # Output: ''
echo ${myArr2[3]}  # Output: 'four'
 

Loop Through Array Elements

 
myStrings='string1 string2 string3'
myStringArray=( ${myStrings} )
for myString in "${myStringArray[@]}"
do
  echo "${myString}"
done
 

References

http://tldp.org/LDP/abs/html/arrays.html

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Bash References

http://tldp.org/LDP/Bash-Beginners-Guide/html/
http://www.linuxconfig.org/Bash_scripting_Tutorial

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Shell script: display tab character

sed -n l file

tab character displayed as ">" character.

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