While [ condition ]

while [ condition ]

• while [ condition ]

• do

• command(s)

• done

$ cat wake

• $ cat wake

• #!/bin/sh

• resp="n"

• while [ "$resp" != "y" ]

• do

• echo "Wakeup [y/n]? "

• read resp

• done

• $

$ cat fac

• $ cat fac

• #!/bin/sh

• echo "Enter number: "

• read num

• fac=1

• loop=1

• while [ $loop -le $num ]

• do

• fac=`expr $fac \* $loop`

• loop=`expr $loop + 1`

• done
• echo "The factorial of $num is $fac"
• $

$ cat lines

• $ cat lines

• while [ "$input" != done ]

• do

• echo 'Enter a filename, or "done":'
• read input
• if [ "$input" != done ]
• then
• lines=`wc –l < $input`
• echo "$input has $lines lines"
• fi

• done

• $

$ cat sayhi

• $ cat sayhi

• #! /bin/sh

• # $* = list of names

• count=$#

• while [ count -gt 0 ]

• do

• echo Hello $1

• count=`expr $count - 1`

• shift

• done

• exit 0

• $

Write a shell script called up, that will move you up in the directory structure

• Write a shell script called up, that will move you up in the directory structure

• If no arguments, move up ONE directory
• If one argument, it should be a number, telling how many directories to move up

• Usage Example:

• $ pwd
• /usr/home/faculty/small000
• $ . up 2
• $ pwd
• /usr/home
• $ . up
• $ pwd
• /usr

#! /bin/sh

• #! /bin/sh

• # $1 = number of levels to go up

• # (if no parameters, go up one level)

• #

• if [ $# -eq 0 ]

• then

• count=1

• else

• count=$1

• fi

• while [ $count -gt 0 ]

• do

• cd ..

• count=`expr $count - 1`

• done

• exit 0

The for statement is used to repeat commands for known or “fixed” values

• The for statement is used to repeat commands for known or “fixed” values

• Unlike C programming, the for loop usually repeats tasks for “arguments” that are either issued from the script or a stated directory after for statement.

for variable in list

• for variable in list

• do

• command(s)

• done

$ cat colorscript

• $ cat colorscript

• #!/bin/sh

• for color in red yellow blue

• do

• echo $color

• done

• echo "the end"

• $ colorscript

• red

• yellow

• blue

• the end

• $

$ userdirs jmsmith krjones

• $ userdirs jmsmith krjones

• Directory listing for: jmsmith

• cprogs/ dotask* xfile

• diskfile mbox

• Directory listing for: krjones

• mbox prog1.c prog2.c

• $

$ printall letter1 names

• $ printall letter1 names

• Print letter1 [y/n]?
• y
• Print names [y/n]?
• n

case string in

• case string in

• choice) command(s)

• ;;

• choice) command(s)

• ;;

• esac

echo Enter command and filename

• echo Enter command and filename

• read cmd file

• case "$cmd" in

• list)
• ls -l "$file"
• ;;
• count)
• wc -l "$file"
• ;;
• *)
• echo "command $cmd is not implemented"
• ;;

• esac

$ cat yesno

• $ cat yesno

• #! /bin/sh

• echo –n 'Yes or No (y/n)? '

• read choice

• case $choice in

• "Y" | "y") echo You chose Yes;;

• "N" | "n") echo You chose No;;

• *) echo Invalid choice;;

• esac

• exit

• $

The following will be a script to:

• The following will be a script to:

• Give user a choice of what to do with the files listed as arguments:

• Copy to a subdirectory

• Concatonate

• or Delete

• Carry out the action chosen, prompting for the subdirectory or file to concatonate into, as needed.

• Display a message confirming action was done.

$ cat files

• $ cat files

• #! /bin.ksh

• # script parameters = files to operate on

• cat << STOP

• M) Move Files

• C) Concatonate Files

• D) Delete Files

• Enter choice:

• STOP

• read choice

• (Continued on next slide)

case $choice in

• case $choice in

• "m"|"M") echo Move files to which subdir?

• read subname

• if [ ! -d $subname ]

• then

• mkdir $subname

• fi

• mv $* $subname

• echo Files moved to subdir $subname

• ;;

• "c"|"C") echo File to place concatonation in?

• read fname

• if [ -f $fname ]

• then

• echo Error - $fname already exists

• else

• cat $* > $fname

• echo Files concated into $fname

• fi

• ;;

"d"|"D") rm $*

• "d"|"D") rm $*

• echo Files $* have been deleted

• ;;

• *) echo Invalid Choice -- No Can Do

• ;;

• esac

• exit 0

• $

The shell searches a list of directories for an executable file with the same name as the command given.

• The shell searches a list of directories for an executable file with the same name as the command given.

• The list of directories is stored in the PATH variable $ PATH=/bin:$PATH (sh/ksh)

• If there is a match in more than one directory, the shell uses the first one it finds.

• To run a command not in one of these directories, give a pathname (relative or absolute) instead.

• $ ~/progs/dosomething

Some commands are built into the shell kernel.

• Some commands are built into the shell kernel.

• The echo command, for example, is often builtin, for efficiency.

• You can find out where the shell is getting a particular command using the “which” command in any shell:

• $ which echo
• echo: shell built-in command.
• $ which cat
• /usr/bin/cat
• $

Predefined Environmental Variables:

• Predefined Environmental Variables:

• PPID shell’s parent’s process id

• IFS list of command line word delimiters (default is list is space, tab & newline)

• PS1 your shell prompt (default is $)

• PS2 your input prompt (default is >)

• SHENV directory where your .profile is located (default is $HOME)

System-wide login file

• System-wide login file

• /etc/profile

• Personal login file

• $HOME/.profile

• Personal environment file

• Set by $ENV
• Usually $HOME/.kshrc

# Set PATH

• # Set PATH

• PATH=$PATH:.

• export PATH

• # Set environmental variable file

• ENV=$HOME/.envsetup

• # Set shell variables

• PS1='Command? '

• # Display status information

• date

• echo "Currently logged in users:“

• users

To include directory in prompt, put these lines in your .profile file:

• To include directory in prompt, put these lines in your .profile file:

• PS1='$PWD $ '

• or

• PS1="`pwd`$ "

• export PS1