Read command and user inputs
The read command in Linux is a shell built-in that allows you to read a line of input from the terminal. It is often used in shell scripts to prompt the user for input or to read input from a file or pipe.
Here is the basic syntax for the read command:
read [options] VARIABLE
The read command reads a single line of input and stores it in the specified VARIABLE. The line of input is terminated by a newline character.
Here is an example of using the read command to prompt the user for their name:
echo "Enter your name: "read nameecho "Hello, $name"This script will print “Enter your name: ” and then wait for the user to enter their name. The name that the user enters is stored in the name variable, and then the script prints “Hello, [name]” with the user’s name.
The read command has a number of options that can be used to control its behavior. For example, the -p option allows you to specify a prompt string, and the -t option allows you to specify a timeout for the command. You can use the -d option to specify a delimiter other than a newline, and the -a option allows you to read the input into an array.
| Option | Description |
|---|---|
-a |
Read the input into an indexed array instead of a single variable. |
-d |
Specify a delimiter character other than a newline to terminate the input. |
-p |
Specify a prompt string to be displayed before reading the input. |
-r |
Do not treat backslashes as escape characters. |
-s |
Do not echo the input to the terminal. |
-t |
Specify a timeout in seconds to wait for input. If no input is received within the timeout, the command will exit. |
-u |
Read input from the specified file descriptor (e.g. -u 3 reads from file descriptor 3). |
Here are some examples of using the read command in Linux:
- Prompt the user for their name and store it in a variable:
echo "Enter your name: "
read name
echo "Hello, $name" - Read a list of names from a file and store them in an array:
# Assume the file "names.txt" contains a list of names, one per line
read -a names < names.txt
echo "The names are: ${names[@]}" - Read input from a pipe:
# Assume the command "generate_input" generates a stream of input
generate_input | while read line; do
echo "Received: $line"
done - Read input from the terminal with a timeout of 5 seconds:
echo "Enter your name (5 seconds): "
read -t 5 name if [ -z "$name" ];
then
echo "Timed out!"
else
echo "Hello, $name"
fi - Read input from the terminal without echoing it to the screen:
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-s password
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For more information on the read command and its options, you can consult the man pages or run help read at the command prompt.