HPUX - Shell Programming

shell programming

$ cat a.c

main(){

  for(;;);

} //needs compile, not a shell script

$ cat myprog

# this is the program myprog

date

ls -F 

//shell script

shell script and child process

$ color=blue

$ cat color1

echo You are now running program: color1

echo the value of the variable color is: $color

$ color1

You are now running program: color1

the value of the variable color is:

$ export color        //환경변수화

$ color1

You are now running program: color1

the value of the variable color is: blue

$ cat color4

echo There are $# command line arguments, 인수의 수 

echo They are $*

echo The first command line argument is $1

$ color4 red white blue black

There are 4 command line arguments

They are red white blue black

The first command line argument is red

shift command

Shifts all strings in * left n position

{

$ cat color5

orig_args=$*

echo There are $# command line arguments

echo They are $*

echo Shifting two arguments

shift 2

echo There are $# command line arguments

echo They are $*

echo Shifting two arguments

shift 2; final_args=$*

echo Original arguments are: $orig_args

echo Final arguments are: $final_args

$ color5 A B C D E F G

There are 7 command line arguments

They are A B C D E F G

Shifting two arguments

There are 5 command line arguments

They are C D E F G

Shifting two arguments

Original arguments are: A B C D E F G

Final arguments are: E F G

}

read command

{

$ cat color6

echo This program prompts for user input

echo "Please enter your favorite two colors -> \c"   // 자동 newline 방지 "\c"

read color_a color_b

echo The colors you entered are: $color_b $color_a

$ color6

This program prompts for user input

Please enter your favorite two colors -> black white

The colors you entered are: white black

$ color6

This program prompts for user input

Please enter your favorite two colors -> red blue green  //입력 2개를 초과

The colors you entered are: blue green red                   //color_a=red, color_b=blue green

}

echo and Escape character

\a : Alert character

\b : backspace [ text cursor]

\c  : suppresses the terminating newline

\f

\n  :new Line

\r

\t  :Tab character

\\ :backslash

\nnn

Additional Techiques

#!/usr/bin/"shell_name" define shell script

Debugging mode

$ sh -x color5 A B C D E F G

+ orig_args=A B C D E F G                          //code를read한 부분

+ echo There are 7 command line arguments

There are 7 command line arguments            //terminal에서 표시되는 부분

+ echo They are A B C D E F G

They are A B C D E F G

+ echo Shifting two arguments

Shifting two arguments

+ shift 2

+ echo There are 5 command line arguments

There are 5 command line arguments

+ echo They are C D E F G

They are C D E F G

+ echo Shifting two arguments

Shifting two arguments

+ shift 2

+ final_args=E F G

+ echo Original arguments are: A B C D E F G

Original arguments are: A B C D E F G

+ echo Final arguments are: E F G

Final arguments are: E F G

Exercise

echo welcome $(whoami)

date

who

echo "\n\n"

who am i | tr -s " " | cut -f1,2 -d" "

echo bye bye

========

grep user /etc/passwd |pr -t -6

echo enter your name:

read usr_name

grep $usr_name /etc/passwd | cut -f6 -d:| ls