A symbol that has the current line number. The search in the if pattern is done with the $. In quotations, we ask perl to print the phrase “New Line with perl” if it reaches the third line. The option tells perl to execute the commands in single quotations. Let’s see how it works: $ perl -e 'print "New Line with perl" if $. For this reason, we need to use a combination of options and if statements to insert a new line into the File1. Perl is a non-interactive command like sed and awk. But since its release 4.1.0, the gawk(GNU awk) command supports the -i option. Notice that with awk we can’t save the results back to the input file. Let’s print the awk_out file: $ cat awk_out Otherwise, awk considers 0 or false by default and just prints the new line and ignores the file1‘s content. We should put any non-zero number after the action section in braces so that awk performs the default action, print, for every line. Also, note that the 1 at the end of the quotation is equivalent to true. Notice we specified the line number with =. Nevertheless, it’s good to know other alternatives. It should be noted that sed is the most common way of inserting. If we check out the content of the sed_out file, we can see that the result is the same as before: $ cat sed_out In this case, we don’t need to use the -i option: $ sed '3 i New Line with sed' File1 > sed_out If we don’t want to change the input file, we can use redirection to save the output to a new file. If we take a look at File1‘s content, we can see that the new line was inserted successfully: $ cat File1 Note that the -i option is only available for GNU sed. Let’s add -i to our previous command: $ sed -i '3 i New Line with sed' File1 If we don’t use this option, sed prints the changes only on the terminal. By using the -i option for sed, we can apply changes directly to the file. “Turtle” is a Python feature like a drawing board, which lets us command a turtle to draw all over it! We can use functions like turtle.forward(…) and turtle.right(…) which can move the turtle around.Changes with ed will save directly to the input file, but with sed, we need an option to save the result to the primary file.
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