read

Read standard input into a variable.

read variable_name

Use the -p option to display a prompt and accept input.

read -p "Enter input: " variable_name

Use the -s option to hide input as it is typed (useful for passwords).

read -s -p "Password: " variable_name

Use the -a option to read input into an array.

read -a array_name

Process a file line by line with a while loop.

while read line; do
    echo "$line"
done < filename

Use the -p option to display a prompt and accept input.

sample_read_name.sh

read -p "Enter your name: " name
echo "Hello, ${name}!"

Run the following command:

bash read_name.sh
Enter your name: Yagami Iori
Hello, Yagami Iori!

Use the -s option to hide input as it is typed. This is useful for password entry.

sample_read_password.sh

read -s -p "Password: " password
echo ""
echo "Password accepted (length: ${#password})"

Run the following command:

bash read_password.sh
Password:
Password accepted (length: 8)

Use the -t option to set a timeout. If no input is received within the specified number of seconds, the command returns exit status 1.

sample_read_timeout.sh

read -t 10 -p "Continue? [y/N]: " answer
if [ $? -ne 0 ]; then
    echo "Timed out. Aborting."
    exit 1
fi
[ "$answer" = "y" ] || { echo "Aborted."; exit 0; }

Run the following command:

bash read_timeout.sh
Continue? [y/N]: y

Use the -a option to read space-separated input into an array.

sample_read_array.sh

read -p "Enter members (space-separated): " -a members
echo "First: ${members[0]}"
echo "All: ${members[@]}"

Run the following command:

bash read_array.sh
Enter members (space-separated): Iori Kyo Terry
First: Iori
All: Iori Kyo Terry

Read a file line by line. Use IFS= to preserve leading and trailing whitespace, and -r to prevent backslash interpretation.

sample_read_file.sh

while IFS= read -r line; do
    echo "Line: $line"
done < /etc/hosts

Run the following command:

bash read_file.sh
Line: 127.0.0.1   localhost
Line: ::1         localhost

You can process piped input the same way.

sample_read_pipe.sh

ls /var/log/*.log | while read -r logfile; do
    size=$(wc -l < "$logfile")
    echo "$logfile: ${size} lines"
done

Run the following command:

bash read_pipe.sh
/var/log/syslog.log: 1520 lines
/var/log/auth.log: 340 lines

Common Mistake 1: Without -r, backslashes in the input are consumed

Without -r, read interprets backslash sequences. A line ending with \ is joined with the next line.

echo "path\\to\\file" | while read line; do echo "$line"; done
path\to\file
（backslash pairs are collapsed）

Always use -r to read input literally.

echo "path\\to\\file" | while read -r line; do echo "$line"; done
path\\to\\file

Common Mistake 2: Without IFS=, leading and trailing whitespace is stripped

By default, read strips leading and trailing whitespace from each line. This can alter data that uses significant spaces.

echo "  hello  " | while read line; do echo "[$line]"; done
[hello]
（leading and trailing spaces removed）

Set IFS= before read to preserve all whitespace.

echo "  hello  " | while IFS= read -r line; do echo "[$line]"; done
[  hello  ]

When reading a file line by line, while IFS= read -r line is the standard idiom. IFS= preserves leading and trailing whitespace, and -r prevents backslash sequences from being interpreted as escape characters.

The -t option sets a timeout so a script does not hang waiting for input indefinitely. Combining -s and -p for password input is a common pattern in installer scripts. For more on loops, see while / until.