Bash Scripting - Write Output of Bash Command into Log File

Let there are some situations in which you have to save your output in a file ( generally called log file). Output can be user details ( username, password, Gmail, etc. ), products record ( buying or selling any goods ), or simply any kind of data that you can store in a log file. 

Let see how to write the output of the bash command into a log file.

Example 1 :

In this example, we can store the names of two-person in a log file.

First, create a log file named " Log.txt " by the following command 

$ touch Log.txt

Note: " Log.txt " will store the output.

Now, create a bash script file by the following command

$ touch Name.sh

Note: " Name.sh " It is a bash script file that will take two names from the user and store it into " Log.txt "

Now, open " Name.sh " in a text editor 

$ nano Name.sh

Now write the following bash script in " Name.sh " 

#!/bin/bash
echo "Enter First Person Name : "

# It will take input from user i.e.
# First Person Name
read FName

# It store First Person Name in Log.txt
echo "First Person Name : $FName">Log.txt
echo
echo "Enter Second Person Name : "

# It will take input from user i.e. 
# Second Person Name
read SName

# It append Second Person Name in Log.txt
echo "Second Person Name : $SName">>Log.txt

Note: Here, ' > ' it will create a new file with a specified name if the file does not exist and it will use to overwrite the data stored in the file ( i.e. " Log.txt "). And ' >> ' it will create a new file with a specified name if the file does not exist and it will append the output data in the file ( i.e. " Log.txt " )

Now save and run " Name.sh " by the following command

$ chmod +x ./Name.sh
$ ./Name.sh

Output : 

As it is shown in the above picture that we take two inputs " Sahil " and " Rakesh ". The output name will store in " Log.txt ".

The above picture shows the " Log.txt " file that the output will store in the log file ( i.e. " Log.txt " ).

Example 2 :

In this example, we can store the student details

First, create a log file named " Student_log.txt " to store output using the below command

$ touch Student_log.txt

Now, create a bash script file by the following command

$ touch Student_details.sh

Now, open " Student_details.sh " in text editor

$ nano Student_details.sh

Now, write the following bash script in " Student_details.sh " 

#!/bin/bash


# Save Date and Time of the bash script
# execution inside Student_log.txt
date>Student_log.txt

echo
echo "Student Details">>Student_log.txt 

echo "Name Of Student : "
read Name

# Store Name in Student_log.txt
echo "Student Name : $Name">>Student_log.txt
echo
echo "Roll No. Of Student : "
read RNo

# Store Roll No. in Student_log.txt
echo "Roll No. : $RNo">>Student_log.txt
echo
echo "Marks Obtained : "
read OMarks
echo "Total Marks : "
read TMarks

# calculate Percentage 
Percentage=$((OMarks*100/TMarks))

# Here it store Percentage in Student_log.txt
echo "Percentage : $Percentage">>Student_log.txt

Note:  Here " date " command will show the date as well as the time of the execution of the " date " command

Now save and run " Student_details.sh " by the following command

$ chmod +x ./Student_details.sh
$ ./Student_details.sh

Output : 

As it is shown in the above picture that we store the date of program execution and student details as well as their percentage. The output will store in " Student_log.txt ".

The above picture is show " Student_log.txt "

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Article Tags :

• Linux-Unix
• Bash-Script