Shell script之if...then

1　　Variable in shell 

　　If you want to print variable, then use echo command.

　　In front of the variable to add $variabel or use ${variable} to fetch the value of variable.

# echo $variable

# echo $PATH

 

2　　if....then 

if condition

then

    condition is true

    execute all commands up to else statement

else

    if condition is not true then

    execute all commands up to fi

fi

 

3　　Example 

 1 #!/bin/bash

 2 # ----------------------------------------------------------------------------

 3 # call pythonscript, then modelsim

 4 # -----------------------------------------------------------------------------

 5 

 6 if [ $# -eq 0 ]; then

 7     here=$PWD;

 8     cd '../../02_modelsim'　　# work directory in your project

 9     vsim -gui&

10     cd $here;

11 elif [ $1 == "-h" ]; then

12     # questasim-doc: 

13     evince /Software/AMS/current/questasim/v10.3b/docs/pdfdocs/_bk_questa_sim.pdf &

14 fi

 

4　　Explanation

`$` refer to `value of` and `#` refer to `number of / total number`

So together

`$#` refer to `The value of the total number of command line arguments passed.`

Thus, you can use $# to check the number of arguments/parameters passed like you did and handle any unexpected situations.

`$1` for `value of 1st argument passed` `$2` for 'value of 2nd argument passed`