Question

I a new to bash but I am trying to write a bash script which does the following:

write_to_file()
{
 #check if file exists
 # if not create the file
 # else open the file to edit
 # go in a while loop
 # ask input from user 
 # write to the end of the file
 # until user types  ":q"

 }

If anyone can point out the literature, I would be very thankful
Thanks

Answer 1

Update: As it’s a bash question, you should try this first. 😉

cat <<':q' >> test.file

To understand what is going on, read about bash’s IO redirection, heredoc syntax and the cat command

---

As you see above, there are many ways to do it. To explain some more bash commands I’ve prepared the function also in the way you’ve requested it:

#!/bin/bash

write_to_file()
{

     # initialize a local var
     local file="test.file"

     # check if file exists. this is not required as echo >> would 
     # would create it any way. but for this example I've added it for you
     # -f checks if a file exists. The ! operator negates the result
     if [ ! -f "$file" ] ; then
         # if not create the file
         touch "$file"
     fi

     # "open the file to edit" ... not required. echo will do

     # go in a while loop
     while true ; do
        # ask input from user. read will store the 
        # line buffered user input in the var $user_input
        # line buffered means that read returns if the user
        # presses return
        read user_input

        # until user types  ":q" ... using the == operator
        if [ "$user_input" = ":q" ] ; then
            return # return from function
        fi

        # write to the end of the file. if the file 
        # not already exists it will be created
        echo "$user_input" >> "$file"
     done
 }

# execute it
write_to_file