Department of Engineering

University of Cambridge >  Engineering Department >  computing help

Answers to examples

Note that these script begin with a line saying #!/bin/sh. This will force the script to be interpreted by the Posix shell even if the user is using another, incompatible, type of shell. Your system might require a different initial line. If you leave the line out, the user's current shell will be used.

• Arguments

  #!/bin/sh
  if [ $# = 1 ]
  then
     string="It is "
     ending=""
  else 
     string="They are "
     ending="s"
  fi
  echo This $0 command has $# argument${ending}.
  if [ $# != 0 ]
  then
  echo $string $*
  fi
  

• Adding Numbers

  #!/bin/sh
  echo "input a number"
  read number1
  
  echo "now input another number"
  read number2
  
  let answer=$number1+$number2
  echo "$number1 + $number2 = $answer"
  

• Login Counting Script

  #!/bin/sh
  times=$(who | grep $1 | wc -l)
  echo "$1 is logged on $times times."
  

• List Directories

  #!/bin/sh
  for file in $*
  do
    if [ -d $file ]
    then
       ls $file
    fi
  done
  

• See Script

  #!/bin/sh
  for file in $*
  do
    if [ -d $file ]
    then
       echo "using ls"
       ls $file
    else
       more $file
    fi
  done
  

• Word-length script

  #!/bin/sh
  echo "Type a word"
  read word
  echo $word is $(echo -n $word | wc -c) letters long
  echo or $word is ${#word} letters long
  

• Safe Copying

  #!/bin/sh
  if [ -f $2 ]
  then
          echo "$2 exists. Do you want to overwrite it? (y/n)"
          read yn
          if [ $yn = "N" -o $yn = "n" ]
          then
              exit 0
          fi
  fi
  cp $1 $2
  

• Mailmerge

  #!/bin/sh
  for name in $(<names)
  do
    sed s/NAME/$name/ <template >letter
    # here you could print the letter file out
  done