This is a multipart blog article series where I am going to explain the concepts of shell scripting and how to write a shell script in Linux, UNIX or Mac based systems. You can also follow this tutorial blog using windows but for that you have to install a bash from.

In this article we are going to understand for loop in shell scripting.

1. The syntax for loop. There are many ways to write the for loop.
   • First way

       for <variable_name> in 1 2 3 4 5 . . N
       do
           command1
           command2
           command3
       done
     

   • Second way

       for <variable_name> in file1 file2 file3
       do
           command1 on $<variable_name>
           command2
           commandN
       done
     

   • Third way

       for <variable_name> in $(Linux-Or-Unix_Command_Here)
       do
           command1 on $<variable_name>
           command2 on $<variable_name>
           commandN
       done
     

   • Forth way

       for (( EXP1; EXP2; EXP3 ))
       do
           command1
           command2
           command3
       done
     

2. We can give the range to iterate like this {1..10}. Here the range is from 1 to 10
3. If we want to specify increment than we can do that in this way {1..10..2}. Here the range is from 1 to 10 and increment will be of 2
4. You can use the above methods only if your bash version is above 4.0. You can check you bash version by this command echo ${BASH_VERSION}

Reference code file for this article

So this was a brief introduction of for loop. Hope you liked it and learned something new form it.

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