bash script example

https://www.shellscript.sh/index.html
https://linuxconfig.org/bash-scripting-tutorial
https://www.tecmint.com/basic-shell-programming-part-ii/


#example1
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first.sh
#!/bin/sh
# This is a comment!
echo Hello World        # This is a comment, too!

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$ chmod 755 first.sh
$ ./first.sh
Hello World
$

#example2
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#!/bin/bash

# example of using arguments to a script
echo "My first name is $1"
echo "My surname is $2"
echo "Total number of arguments is $#"

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$ chmod a+x name.sh
$ ./name.sh Hans-Wolfgang Loidl
My first name is Hans-Wolfgang
My surname is Loidl
Total number of arguments is 2

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#!/bin/bash
#Declare array with 4 elements
ARRAY=( 'Debian Linux' 'Redhat Linux' Ubuntu Linux )
# get number of elements in the array
ELEMENTS=${#ARRAY[@]}

# echo each element in array
# for loop
for (( i=0;i<$ELEMENTS;i++)); do
    echo ${ARRAY[${i}]}
done


#example3
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#!/bin/bash
# declare integers
NUM1=2
NUM2=2
if [ $NUM1 -eq $NUM2 ]; then
    echo "Both Values are equal"
else
    echo "Values are NOT equal"
fi


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#!/bin/bash
file="./file"
if [ -e $file ]; then
    echo "File exists"
else
    echo "File does not exists"
fi



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#!/bin/bash
 
echo '### let ###'
# bash addition
let ADDITION=3+5
echo "3 + 5 =" $ADDITION

# bash subtraction
let SUBTRACTION=7-8
echo "7 - 8 =" $SUBTRACTION

# bash multiplication
let MULTIPLICATION=5*8
echo "5 * 8 =" $MULTIPLICATION

# bash division
let DIVISION=4/2
echo "4 / 2 =" $DIVISION

# bash modulus
let MODULUS=9%4
echo "9 % 4 =" $MODULUS

# bash power of two
let POWEROFTWO=2**2
echo "2 ^ 2 =" $POWEROFTWO


echo '### Bash Arithmetic Expansion ###'
# There are two formats for arithmetic expansion: $[ expression ]
# and $(( expression #)) its your choice which you use

echo 4 + 5 = $((4 + 5))
echo 7 - 7 = $[ 7 - 7 ]
echo 4 x 6 = $((3 * 2))
echo 6 / 3 = $((6 / 3))
echo 8 % 7 = $((8 % 7))
echo 2 ^ 8 = $[ 2 ** 8 ]


echo '### Declare ###'

echo -e "Please enter two numbers \c"
# read user input
read num1 num2
declare -i result
result=$num1+$num2
echo "Result is:$result "

# bash convert binary number 10001
result=2#10001
echo $result

# bash convert octal number 16
result=8#16
echo $result

# bash convert hex number 0xE6A
result=16#E6A
echo $result


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#!/bin/bash
# Simple linux bash calculator
echo "Enter input:"
read userinput
echo "Result with 2 digits after decimal point:"
echo "scale=2; ${userinput}" | bc
echo "Result with 10 digits after decimal point:"
echo "scale=10; ${userinput}" | bc
echo "Result as rounded integer:"
echo $userinput | bc



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#!/bin/bash
# Counting the number of lines in a list of files
# for loop over arguments

if [ $# -lt 1 ]
then
  echo "Usage: $0 file ..."
  exit 1
fi

echo "$0 counts the lines of code"
l=0
n=0
s=0
for f in $*
do
    l=`wc -l $f | sed 's/^\([0-9]*\).*$/\1/'`
    echo "$f: $l"
        n=$[ $n + 1 ]
        s=$[ $s + $l ]
done

echo "$n files in total, with $s lines in total"

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#!/bin/bash
# Counting the number of lines in a list of files
# function version

count_lines () {
  local f=$1  
  # this is the return value, i.e. non local
  l=`wc -l $f | sed 's/^\([0-9]*\).*$/\1/'`
}

if [ $# -lt 1 ]
then
  echo "Usage: $0 file ..."
  exit 1
fi

echo "$0 counts the lines of code"
l=0
n=0
s=0
while [ "$*" != ""  ]
do
        count_lines $1
        echo "$1: $l"
        n=$[ $n + 1 ]
        s=$[ $s + $l ]
    shift
done

echo "$n files in total, with $s lines in total"

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#!/bin/bash
# Counting the number of lines in a list of files
# function version using return code
# WRONG version: the return code is limited to 0-255
#  so this script will run, but print wrong values for
#  files with more than 255 lines

count_lines () {
  local f=$1  
  local m
  m=`wc -l $f | sed 's/^\([0-9]*\).*$/\1/'`
  return $m
}

if [ $# -lt 1 ]
then
  echo "Usage: $0 file ..."
  exit 1
fi

echo "$0 counts the lines of code"
l=0
n=0
s=0
while [ "$*" != ""  ]
do
        count_lines $1
    l=$?
        echo "$1: $l"
        n=$[ $n + 1 ]
        s=$[ $s + $l ]
    shift
done

echo "$n files in total, with $s lines in total"

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~~~~Count only files we own
#!/bin/bash
# Counting the number of lines in a list of files
# for loop over arguments
# count only those files I am owner of

if [ $# -lt 1 ]
then
  echo "Usage: $0 file ..."
  exit 1
fi

echo "$0 counts the lines of code"
l=0
n=0
s=0
for f in $*
do
  if [ -O $f ] # checks whether file owner is running the script
  then
      l=`wc -l $f | sed 's/^\([0-9]*\).*$/\1/'`
      echo "$f: $l"
      n=$[ $n + 1 ]
      s=$[ $s + $l ]
  else
      continue
  fi
done

echo "$n files in total, with $s lines in total"

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#!/bin/bash
date;
echo "uptime:"
uptime
echo "Currently connected:"
w
echo "--------------------"
echo "Last logins:"
last -a |head -3
echo "--------------------"
echo "Disk and memory usage:"
df -h | xargs | awk '{print "Free/total disk: " $11 " / " $9}'
free -m | xargs | awk '{print "Free/total memory: " $17 " / " $8 " MB"}'
echo "--------------------"
start_log=`head -1 /var/log/messages |cut -c 1-12`
oom=`grep -ci kill /var/log/messages`
echo -n "OOM errors since $start_log :" $oom
echo ""
echo "--------------------"
echo "Utilization and most expensive processes:"
top -b |head -3
echo
top -b |head -10 |tail -4
echo "--------------------"
echo "Open TCP ports:"
nmap -p- -T4 127.0.0.1
echo "--------------------"
echo "Current connections:"
ss -s
echo "--------------------"
echo "processes:"
ps auxf --width=200
echo "--------------------"
echo "vmstat:"
vmstat 1 5


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MAX=95
EMAIL=[e-mail]
PART=sda1
USE=`df -h |grep $PART | awk '{ print $5 }' | cut -d'%' -f1`
if [ $USE -gt $MAX ]; then
echo "Percent used: $USE" | mail -s "Running out of disk space" $EMAIL
fi

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#!/usr/bin/env bash
set -e

remote_list() {
  local bash_list=$(2>/dev/null curl -l 'ftp://ftp.gnu.org/gnu/bash/' | grep '^bash-.*.tar.gz$' | grep -v -- '-doc-')
  local version
  for version in $bash_list; do
    echo ${version%.tar.gz}
  done
}

current_version() {
  local current_bash_path=$(which bash)
  if [[ "$current_bash_path" =~ $BASHVM_HOME/usr/bash- ]]; then
    # current version is in bashvm
    local current=${current_bash_path#$BASHVM_HOME/usr/bash-}
    current=${current%/bin/bash}
    echo $current
  else
    # current version is system
    echo 'system'
  fi
}

local_list() {
  local current=$(current_version)
  local fullpath;
  ls -Ad $BASHVM_HOME/usr/* >/dev/null 2>&1 || exit 0
  echo
  for fullpath in $BASHVM_HOME/usr/*; do
    local version=$(basename $fullpath)
    version=${version#bash-}
    if [[ "$version" == "$current" && "$version" == "$bashvm_default_version" ]]; then
      echo "=* bash-$version"
    elif [[ "$version" == "$bashvm_default_version" ]]; then
      echo " * bash-$version"
    elif [[ "$version" == "$current" ]]; then
      echo "=> bash-$version"
    else
      echo "   bash-$version"
    fi
  done
  echo
  echo "# => - current"
  echo "# =* - current && default"
  echo "#  * - default"
}

help() {
  cat <<EOF
Usage: bashvm list [command]
Avairable commands for bashvm list
  local     Show installed bash list in local (default)
  remote    Show bash list which able to install
EOF
}

if [[ $# -eq 0 ]]; then
  local_list
  exit 0
fi

case "$1" in
remote)
  remote_list
  ;;
local)
  local_list
  ;;
--help)
  shift
  help
  ;;
-*|--*)
  bashvm_die "Unrecognized option: $1"
  exit 1
  ;;
*)
  bashvm_die "Unrecognized command: $1"
  exit 1
  ;;
esac

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