Downloaded 32 times
![10
Condition
test or ‘ [ ‘
if test –f fred.c
then
...
fi
If [ -f
fred.c ]
then
...
fi
if [ -f fred.c ];then
...
fi
expression1 –eq expression2
expression1 –ne expression2
expression1 –gt expression2
expression1 –ge expression2
expression1 -lt expression2
expression1 –le expression2
!expression
-d file if directory
-e file if exist
-f file if file
-g file if set-group-id
-r file if readable
-s file if size >0
-u file if set-user-id
-w file if writable
-x file if executableString1 = string2
String1 != string 2
-n string (if not empty string)
-z string (if empty string)
need space !](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/85/Module-03-Programming-on-Linux-10-320.jpg)
![11
Control Structure
Syntax
if condition
then
statement
else
statement
fi
#!/bin/sh
echo “Is it morning? Please answer yes or no”
read timeofday
if [ $timeofday = “yes” ]; then
echo “Good morning”
else
echo “Good afternoon”
fi
exit 0
Is it morning? Please answer yes or no
yes
Good morning](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/85/Module-03-Programming-on-Linux-11-320.jpg)
![12
Condition Structure
#!/bin/sh
echo “Is it morning? Please answer yes or no”
read timeofday
if [ $timeofday = “yes” ]; then
echo “Good morning”
elif [ $timeofday = “no” ]; then
echo “Good afternoon”
else
echo “Sorry, $timeofday not recongnized. Enter yes or no”
exit 1
fi
exit 0](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/85/Module-03-Programming-on-Linux-12-320.jpg)
![13
Condition Structure
#!/bin/sh
echo “Is it morning? Please answer yes or no”
read timeofday
if [ “$timeofday” = “yes” ]; then
echo “Good morning”
elif [ $timeofday = “no” ]; then
echo “Good afternoon”
else
echo “Sorry, $timeofday not recongnized. Enter yes or no”
exit 1
fi
exit 0
If input “enter” still returns Good morning](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/85/Module-03-Programming-on-Linux-13-320.jpg)
![16
Loop Structure
Syntax
while condition
do
statement
done
#!/bin/sh
for foo in 1 2 3 4 5 6 7 8 9 10
do
echo “here we go again”
done
exit 0
#!/bin/sh
foo = 1
while [ “$foo” –le 10 ]
do
echo “here we go again”
foo = $foo(($foo+1))
done
exit 0
Syntax
until condition
do
statement
done
Note: condition is
Reverse to while
How to re-write
previous sample?](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/85/Module-03-Programming-on-Linux-16-320.jpg)
![17
Case Statement
Syntax
case variable in
pattern [ | pattern ] …) statement;;
pattern [ | pattern ] …) statement;;
…
esac
#!/bin/sh
echo “Is it morning? Please answer yes or no”
read timeofday
case “$timeofday” in
yes) echo “Good Morning”;;
y) echo “Good Morning”;;
no) echo “Good Afternoon”;;
n) echo “Good Afternoon”;;
* ) echo “Sorry, answer not recongnized”;;
esac
exit 0](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/85/Module-03-Programming-on-Linux-17-320.jpg)
![24
Pattern Matching
grep print lines matching a pattern
(General Regular Expression Parser)
grep [options] PATTERN [FILES]
option
-c print number of output context
-E Interpret PATTERN as an extended regular expression
-h Supress the prefixing of filenames
-i ignore case
-l surpress normal output
-v invert the sense of matching
% grep in words.txt
% grep –c in words.txt words2.txt
% grep –c –v in words.txt words2.txt](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/85/Module-03-Programming-on-Linux-24-320.jpg)
![10
Condition
test or ‘ [ ‘
if test –f fred.c
then
...
fi
If [ -f
fred.c ]
then
...
fi
if [ -f fred.c ];then
...
fi
expression1 –eq expression2
expression1 –ne expression2
expression1 –gt expression2
expression1 –ge expression2
expression1 -lt expression2
expression1 –le expression2
!expression
-d file if directory
-e file if exist
-f file if file
-g file if set-group-id
-r file if readable
-s file if size >0
-u file if set-user-id
-w file if writable
-x file if executableString1 = string2
String1 != string 2
-n string (if not empty string)
-z string (if empty string)
need space !](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/75/Module-03-Programming-on-Linux-10-2048.jpg)
![11
Control Structure
Syntax
if condition
then
statement
else
statement
fi
#!/bin/sh
echo “Is it morning? Please answer yes or no”
read timeofday
if [ $timeofday = “yes” ]; then
echo “Good morning”
else
echo “Good afternoon”
fi
exit 0
Is it morning? Please answer yes or no
yes
Good morning](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/75/Module-03-Programming-on-Linux-11-2048.jpg)
![12
Condition Structure
#!/bin/sh
echo “Is it morning? Please answer yes or no”
read timeofday
if [ $timeofday = “yes” ]; then
echo “Good morning”
elif [ $timeofday = “no” ]; then
echo “Good afternoon”
else
echo “Sorry, $timeofday not recongnized. Enter yes or no”
exit 1
fi
exit 0](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/75/Module-03-Programming-on-Linux-12-2048.jpg)
![13
Condition Structure
#!/bin/sh
echo “Is it morning? Please answer yes or no”
read timeofday
if [ “$timeofday” = “yes” ]; then
echo “Good morning”
elif [ $timeofday = “no” ]; then
echo “Good afternoon”
else
echo “Sorry, $timeofday not recongnized. Enter yes or no”
exit 1
fi
exit 0
If input “enter” still returns Good morning](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/75/Module-03-Programming-on-Linux-13-2048.jpg)
![16
Loop Structure
Syntax
while condition
do
statement
done
#!/bin/sh
for foo in 1 2 3 4 5 6 7 8 9 10
do
echo “here we go again”
done
exit 0
#!/bin/sh
foo = 1
while [ “$foo” –le 10 ]
do
echo “here we go again”
foo = $foo(($foo+1))
done
exit 0
Syntax
until condition
do
statement
done
Note: condition is
Reverse to while
How to re-write
previous sample?](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/75/Module-03-Programming-on-Linux-16-2048.jpg)
![17
Case Statement
Syntax
case variable in
pattern [ | pattern ] …) statement;;
pattern [ | pattern ] …) statement;;
…
esac
#!/bin/sh
echo “Is it morning? Please answer yes or no”
read timeofday
case “$timeofday” in
yes) echo “Good Morning”;;
y) echo “Good Morning”;;
no) echo “Good Afternoon”;;
n) echo “Good Afternoon”;;
* ) echo “Sorry, answer not recongnized”;;
esac
exit 0](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/75/Module-03-Programming-on-Linux-17-2048.jpg)
![24
Pattern Matching
grep print lines matching a pattern
(General Regular Expression Parser)
grep [options] PATTERN [FILES]
option
-c print number of output context
-E Interpret PATTERN as an extended regular expression
-h Supress the prefixing of filenames
-i ignore case
-l surpress normal output
-v invert the sense of matching
% grep in words.txt
% grep –c in words.txt words2.txt
% grep –c –v in words.txt words2.txt](https://image.slidesharecdn.com/module-3programmingonlinux-140329094714-phpapp02/75/Module-03-Programming-on-Linux-24-2048.jpg)
Uploaded byTushar B Kute
Module 03 Programming on Linux
The document is a comprehensive guide on basic shell scripting, covering topics such as the purpose of shell scripts, syntax, variables, control structures, loops, and pattern matching. It includes examples to demonstrate commands and constructs in shell scripting for effective system administration. Additionally, it provides links to further resources like the Bash Beginners Guide.
More Related Content
Similar to Module 03 Programming on Linux
Module 03 Programming on Linux
- 1. 1 Module-3 Basic ShellScripting Tushar B Kute tushar.kute@gmail.com http://snashlug.org contact@snashlug.org
- 2. 2 Why Shell? Thecommercial UNIX used Korn Shell For Linux, the Bash is the default Why Shell? For routing jobs, such as system administration, without writing programs However, the shell script is not efficient, therefore, can be used for prototyping the ideas For example, % ls –al | more (better format of listing directory) % man bash | col –b | lpr (print man page of man)
- 3. 3 What is Shell? Shell is the interface between end user and the Linux system, similar to the commands in Windows Bash is installed as in /bin/sh Check the version % /bin/sh --version Kernel Other programs X window bash csh
- 4. 4 Shell as aLanguage We can write a script containing many shell commands Interactive Program: grep files with POSIX string and print it % for file in * > do > if grep –l POSIX $file > then > more $file fi done Posix There is a file with POSIX in it ‘*’ is wildcard % more `grep –l POSIX *` % more $(grep –l POSIX *) % more –l POSIX * | more
- 5. 5 Writing a Script Use text editor to generate the “first” file #!/bin/sh # first # this file looks for the files containing POSIX # and print it for file in * do if grep –q POSIX $file then echo $file fi done exit 0 % /bin/sh first % chmod +x first %./first (make sure . is include in PATH parameter) exit code, 0 means successful
- 6. 6 Syntax Variables Conditions Control Lists Functions Shell Commands Result Document
- 7. 7 Variables Variables neededto be declared, note it is case-sensitive (e.g. foo, FOO, Foo) Add ‘$’ for storing values % salutation=Hello % echo $salutation Hello % salutation=7+5 % echo $salutation 7+5 % salutation=“yes sir” % echo $salutation yes sir % read salutation Hello! % echo $salutation Hello!
- 8. 8 Quoting Edit a“vartest.sh” file #!/bin/sh myvar=“Hi there” echo $myvar echo “$myvar” echo `$myvar` echo $myvar echo Enter some text read myvar echo ‘$myvar’ now equals $myvar exit 0 Output Hi there Hi there $myvar $myvar Enter some text Hello world $myvar now equals Hello world
- 9. 9 Environment Variables $HOMEhome directory $PATH path $$ process id of the script $# number of input parameters $0 name of the script file $IFS separation character (white space)
- 10. 10 Condition test or‘ [ ‘ if test –f fred.c then ... fi If [ -f fred.c ] then ... fi if [ -f fred.c ];then ... fi expression1 –eq expression2 expression1 –ne expression2 expression1 –gt expression2 expression1 –ge expression2 expression1 -lt expression2 expression1 –le expression2 !expression -d file if directory -e file if exist -f file if file -g file if set-group-id -r file if readable -s file if size >0 -u file if set-user-id -w file if writable -x file if executableString1 = string2 String1 != string 2 -n string (if not empty string) -z string (if empty string) need space !
- 11. 11 Control Structure Syntax if condition then statement else statement fi #!/bin/sh echo“Is it morning? Please answer yes or no” read timeofday if [ $timeofday = “yes” ]; then echo “Good morning” else echo “Good afternoon” fi exit 0 Is it morning? Please answer yes or no yes Good morning
- 12. 12 Condition Structure #!/bin/sh echo “Isit morning? Please answer yes or no” read timeofday if [ $timeofday = “yes” ]; then echo “Good morning” elif [ $timeofday = “no” ]; then echo “Good afternoon” else echo “Sorry, $timeofday not recongnized. Enter yes or no” exit 1 fi exit 0
- 13. 13 Condition Structure #!/bin/sh echo “Isit morning? Please answer yes or no” read timeofday if [ “$timeofday” = “yes” ]; then echo “Good morning” elif [ $timeofday = “no” ]; then echo “Good afternoon” else echo “Sorry, $timeofday not recongnized. Enter yes or no” exit 1 fi exit 0 If input “enter” still returns Good morning
- 14. 14 Loop Structure Syntax for variable do statement done #!/bin/sh forfoo in bar fud 43 do echo $foo done exit 0 bar fud 43 How to output as bar fud 43? Try change for foo in “bar fud 43” This is to have space in variable
- 15. 15 Loop Structure Usewildcard ‘*’ #!/bin/sh for file in $(ls f*.sh); do lpr $file done exit 0 Print all f*.sh files
- 16. 16 Loop Structure Syntax while condition do statement done #!/bin/sh forfoo in 1 2 3 4 5 6 7 8 9 10 do echo “here we go again” done exit 0 #!/bin/sh foo = 1 while [ “$foo” –le 10 ] do echo “here we go again” foo = $foo(($foo+1)) done exit 0 Syntax until condition do statement done Note: condition is Reverse to while How to re-write previous sample?
- 17. 17 Case Statement Syntax case variablein pattern [ | pattern ] …) statement;; pattern [ | pattern ] …) statement;; … esac #!/bin/sh echo “Is it morning? Please answer yes or no” read timeofday case “$timeofday” in yes) echo “Good Morning”;; y) echo “Good Morning”;; no) echo “Good Afternoon”;; n) echo “Good Afternoon”;; * ) echo “Sorry, answer not recongnized”;; esac exit 0
- 18. 18 Case Statement Amuch “cleaner” version #!/bin/sh echo “Is it morning? Please answer yes or no” read timeofday case “$timeofday” in yes | y | Yes | YES ) echo “Good Morning”;; n* | N* ) echo “Good Afternoon”;; * ) echo “Sorry, answer not recongnized”;; esac exit 0 But this has a problem, if we enter ‘never’ which obeys n* case and prints “Good Afternoon”
- 19. 19 Command expr evaluateexpressions %x=`expr $x + 1` (Assign result value expr $x+1 to x) Also can be written as %x=$(expr $x + 1) Expr1 | expr2 (or) expr1 != expr2 Expr1 & expr2 (and) expr1 + expr2 Expr1 = expr2 expr1 – expr2 Expr1 > expr2 expr1 * expr2 Expr1 >= expr2 expr1 / expr2 Expr1 < expr2 expr1 % expr2 (module) Expr1 <= expr2
- 20. 20 Command printf formatand print data Escape sequence backslash a beep sound b backspace f form feed n newline r carriage return t tab v vertical tab Conversion specifier %d decimal %c character %s string %% print % % printf “%sn” hello Hello % printf “%s %dt%s” “Hi There” 15 people Hi There 15 people
- 21. 21 Command return returna value set set parameter variable #!/bin/sh echo the date is $(date) set $(date) echo The month is $2 exit 0
- 22. 22 Pattern Matching operator ! -nottest reverse -a -and test and -o -or test or action -exec command execute command -ok command confirm and exectute command -print print -ls ls –dils Find files newer than while2 then print % find . –newer while2 -print
- 23. 23 Pattern Matching Find filesnewer than while2 then print only files % find . –newer while2 –type f –print Find files either newer than while2, start with ‘_’ % find . ( -name “_*” –or –newer while2 ) –type f –print Find files newer than while2 then list files % find . –newer while2 –type f –exec ls –l {} ;
- 24. 24 Pattern Matching grepprint lines matching a pattern (General Regular Expression Parser) grep [options] PATTERN [FILES] option -c print number of output context -E Interpret PATTERN as an extended regular expression -h Supress the prefixing of filenames -i ignore case -l surpress normal output -v invert the sense of matching % grep in words.txt % grep –c in words.txt words2.txt % grep –c –v in words.txt words2.txt
- 25. 25 References Bash BeginnersGuide (http://tldp.org/LDP/Bash-Beginners-Guide/)