How to redirect stdin?

You can redirect stdin in several ways, typically using the < operator or by piping (|) the output of one command into another. Here are some common methods:

1. Using Input Redirection with <

You can redirect the contents of a file to stdin using the < operator. For example:

cat < input.txt

This command will read the contents of input.txt and display it using cat.

2. Using Pipe |

You can also use a pipe to send the output of one command as input to another command. For example:

echo "Hello, World!" | grep "Hello"

In this case, the output of echo is sent to grep, which processes it.

3. Using Here Documents

You can use a here document to provide input directly in the command line. For example:

cat << EOF
This is line 1
This is line 2
EOF

This will output the lines between << EOF and EOF.

4. Using File Redirection

You can also redirect the output of a command to a file, which can then be used as input for another command:

echo "Sample text" > output.txt
cat < output.txt

In this example, output.txt is created with "Sample text," and then cat reads from it.

These methods allow you to effectively redirect stdin for various commands in the terminal.