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Bash scripting

Fancy Fish-like Bash

Install ble.sh: 

git clone --recursive https://github.com/akinomyoga/ble.sh.git
make -C ble.sh
source ble.sh/out/ble.sh

What's hogging the port?

ss -lptn 'sport = :9080'

Parse parameters

Source: Using getopts to process long and short command line options

# NOTE: This requires GNU getopt.  On Mac OS X and FreeBSD, you have to install this
# separately; see below.
TEMP=$(getopt -o vdm: --long verbose,debug,memory:,debugfile:,minheap:,maxheap: \
              -n 'javawrap' -- "$@")

if [ $? != 0 ] ; then echo "Terminating..." >&2 ; exit 1 ; fi

# Note the quotes around '$TEMP': they are essential!
eval set -- "$TEMP"

VERBOSE=false
DEBUG=false
MEMORY=
DEBUGFILE=
JAVA_MISC_OPT=
while true; do
  case "$1" in
    -v | --verbose ) VERBOSE=true; shift ;;
    -d | --debug ) DEBUG=true; shift ;;
    -m | --memory ) MEMORY="$2"; shift 2 ;;
    --debugfile ) DEBUGFILE="$2"; shift 2 ;;
    --minheap )
      JAVA_MISC_OPT="$JAVA_MISC_OPT -XX:MinHeapFreeRatio=$2"; shift 2 ;;
    --maxheap )
      JAVA_MISC_OPT="$JAVA_MISC_OPT -XX:MaxHeapFreeRatio=$2"; shift 2 ;;
    -- ) shift; break ;;
    * ) break ;;
  esac
done

Beep when done

./run_long.sh; echo -e "\a"

Bash Strict Mode

Unofficial Strict Mode

Working with processes

Check if a process is running:

ps -p $PID >&-

... returns 0 if the process id exists, and 1 otherwise

  • $! the PID of the last background job run
  • $? the return code of the last job that finished
  • wait $PID blocks until the task completes

Echo multiline string

The example creates a small executable script that dumps the contents of the root dir.

cat <<EOL > listroot.sh
#!/bin/bash
ls -lA /
EOL
chmod +x listroot.sh