Shell Script: Pausing the execution with sleep command

To pause the execution of shell script use sleep command.

Examples:

sleep 1   # Pause for 1 sec
sleep 1s  # Pause for 1 sec
sleep 1m  # Pause for 1 min
sleep 1h  # Pause for 1 hour
sleep 1d  # Pause for 1 day
sleep .1  # Pause for 100 mili-sec i.e. 0.1sec

Thank you

Golang and Shell Script : Execute sh file from Go file and vice-versa.

We will see here today, executing a Go file from Shell script file and vice-versa.

Don't know, how to create and run a shell script file ?
Shell script file name : hello_sh.sh
Content of hello_sh.sh :

echo "Hello, I am inside 'hello_sh.sh' file."
echo "Now, I am going to call 'hello_go.go' file. The output: "
go run hello_go.go

Hello world ! program in Golang.
Go file name : hello_go.go
Content of hello_go.go :

package main
import (
        "bytes"
        "fmt"
        "log"
        "os/exec"
        "strings"
)
func main() {
        fmt.Printf("Hello, I am from 'hello_go.go' file.");
        fmt.Printf("\nNow, I am going to execute 'hello_sh.sh' file\n");
        cmd := exec.Command("bash", "hello_sh.sh");
        cmd.Stdin = strings.NewReader("");
        var out bytes.Buffer;
        cmd.Stdout = &out;
        err := cmd.Run();
        if err != nil {
                log.Fatal(err);
        }
        fmt.Printf("Output \n",out.String());
}

*For beginner change the file name "hello_sh.sh" and  "hello_go.go" according to your requirement.
*For advanced programmer, try this recursion and you can comment your output below.


-Thank you

Shell Script :generating random numbers

Generating random numbers is bit easier as compare to generating random numbers in other languages.

To generate a random number in shell script use below command

$RANDOM

The above command is case sensitive and hence $random will not give you desire result.

Generating  random number with in a range

lr=100 # lower range
ur=600 # upper range
r=`expr $ur - $lr`
echo "The random number of `expr $RANDOM % $r + $lr`"

-Thank you

Shell Script : Reading a file Line by Line in shell script

Reading the file using loop statement

File name : job.txt
File Content :

   Data
   RAM:256 MB
   Bandwidth:1 gbps

Command 1:

        
              while read line
              do
                echo $line
              done <job.txt 

Output :

   Data
   RAM:256 MB
   Bandwidth:1 gbps

Command 2:

        
              for line in $(cat job.txt)
              do
                echo $line
              done <job.txt 

Output :

  
   Data
   RAM:256
   MB
   Bandwidth:1
   gbps

Shell Script : Creating and Running a shell script file

OS : Ubuntu 14.04
Steps are as follows:

Step 1: Open Terminal by pressing ctrl+alt+T

Step 2: Use any editor to create a shell script file. 

       
         Sample 1:  sudo gedit firstShell.sh 
         Sample 2:  sudo vim firstShell.sh 
         Sample 3:  sudo vi firstShell.sh 

Step 3: Enter the following line

        
          echo "I am from firstShell.sh file !!!"  

Now save the file according to the editor you are using.
Step 4: Modify the attribute of the file as executable file

        

         Sample:  sudo chmod +x firstShell.sh  

Step 5: Now RUN the shell script file by entering following command in the terminal

         ./firstShell.sh