Shell Script to Display the Exit Status Using Grep Command

Linux provides users a great cool feature of the command-line tool along with a graphical user interface where they can perform tasks via ruining command. All of this command returns a status according to their execution. Its execution value can be used for showing errors or take some other action in a shell script. 

Exit status is following according to their execution 

• Command was successfully executed:  0 ( value of exit status)
• Command was a failure:  1 – 255 ( value of exit status will be b/w 1 to 255)

Exit status: Every Linux command has exit status after execution. Its value can get by calling $? ( shell variable ). It gives the value of previous executed command. 

Note: Command for printing exit status for previous command:  echo $? 

Here in this article, a shell script will be written to display the exit status using the grep command. It will show an example of shell scripts to display the exit status. 

Approach:

To write the script code for this follow the below steps

1. Use the touch command to create the database which is a text file named gfg.txt.
2. Now get the key from the user if he wants to insert it in the database or check that the book is present in a database or not( means the book has read or not ).
3. Now according to the chosen key make the if-else block and read the book Name from the user.
4. In the first condition check the availability of the book using the grep command and get the exit status value and check if 0 or not. And the second condition simply gets the book name and adds the name to the database.
5. Now, print the status of the book read according to the value of the exit status of the previous command.

Shell Script Code: 

# shell script for display exit status by using grep command

# make an file gfg.txt to contain the book name of user that he has read 
touch gfg.txt 

# now print user to tell him the scenario 
echo "Please, enter the some of your book name that you 
    have read or a book name that you want to know read status of that book"
echo

# print the key to ask user find the book or write the book name
echo "Please enter a key like following"
echo "Enter 1 to know the book read status" 
echo "Enter 2 to write the book name in book database ( gfg.txt )"

# read the entered key
read key
echo

# check the condition using if-else statement
if [[ $key == 1 ]]
then 
    # loop to get the name of book continuously 
    while [ 1 ]
    do
        # print the initial statement
        echo "Enter book name about that you want to know read status or -1 for exit"
        
        # read the book name and find in gfg.text using grep command
        read bookName
        
        # check condition to break the loop
        if [[ $bookName == -1 ]]
        then
            break
        else
        
            # now find the book in gfg.text
            count=$(grep -c "$bookName" gfg.txt)
            
            # get the exit status of the previous command 
            exitStatus=$?
                
            # check the value of exitStatus and print output according that 
            if [[ $exitStatus == 0 ]]
            then 
                # give the msg to user that he have read that book 
                echo "Your previous command exit status is $exitStatus"
                echo "You have read the $bookName book."
                echo 
            else
                # give the msg to user that he didn't read that book yet.
                echo "Your previous command exit status is $exitStatus"
                echo "You didn't read $bookName book yet."
                echo
            fi
            
        fi
    done
    
    
else
    # loop to get the name of books continuously 
    while [ 1 ]
    do
        echo "Enter book name that you want write in database (gfg.txt) or -1 for exit"
        
        # read the name of book
        read bookName
        
        # check the condition to break the loop
        if [[ $bookName != -1 ]]
        then
            # write the book name in text file
            echo $bookName >> gfg.txt
        else
            break
        fi
        echo
    done
fi
        

In the first example will show the inserting book name in the database ( gfg.text). 

In the second example will know about the check the book read status ( internal checking using grep command and exit status):