Shell Tips

1. Quicklinks

2. Reference

() execute command in subshell
{} execute command in currecnt shell Usage is same with () expect the final command in the list ends with a semicolon.

3. Sample Section A

3.1. grep

  grep -Elr --include=*.xsd --exclude-dir={branches,tags} VendorDesc.xsd $DIRECTORY
  ### count process and exclude grep itself
  ps aux | grep vpnc | grep -v grep -c

3.2. find

  find ${1} \( -name Consume*wsdl -o -name Produce*wsdl \) -path *trunk*
  find $update_dir \( -name '*.java' \) \( -path '**/source/**' -o -path '**/test/**' -o -path '**/resource/**' \)

3.3. awk

  ### list all time of each ping
  awk -F"=" '/time=/ {print substr($4,0,length($4)-3) }' < ping.log
  ### passing shell parameter to awk scripts
  svn st ${dirs} | awk -F" " -v ac="${*}" ' /'${predicate}'/ && (index($2,"\\")==0 || gsub(/\\/,"/",$2)) {print ac, $2}'
  ### change Output Row Separator
  awk ' BEGIN { ORS = " " } { print }'

3.4. sed

  ll | sed '/Stores\|Test\|^-\|^t/d' | wc
  smbclient -L \\\\hangzhou2\\twitters -U foobar | sed '/Hangzhou20/,$d'
  export BEA_IP=`/sbin/ifconfig eth0 | sed '/inet addr/!d;s/.*addr:\([^ ]\+\).*/\1/g'`

3.5. cp

  cp filename{,.bak}

4. Sample Section B

4.1. while

  while getopts ":ab:c" opt; do
      case $opt in
      a ) echo "I am a" ;;
      b ) echo $OPTARG  ;;
      c ) echo "i am c" ;;
      ? ) echo "usage : $0 [-a] [-b barg] [-c] args .."
          exit 1 ;;
      esac
      shift $(($OPTIND - 1))
  done

4.2. for

  for s in $(echo $string | sed "s/;/ /g"); do
      echo $s
  done

  for (( i=1; i<=$n; i++ )) do
     ls -1 "${file_pattern}" | sed 's#\(.*\)\(.xml\).bak#cp & \1'"_$i"'\2#g'
  done

4.3. case

  case $action in
      backup ) tar cfj "$backup_dir/$bakfile" * --exclude "jobs/*/workspace" ;;
      rest | restore ) tar xfj $backup_dir/$bakfile ;;
      * ) echo "all supported actions: backup | rest[ore]" ; exit 0 ;;
  esac