Less than

Redirect data to stdin. More information: https://gnu.org/software/bash/manual/bash.html#Redirecting-Input.

• Redirect a file to stdin (achieves the same effect as cat file.txt |):

command < path/to/file.txt

• Create a here document and pass that into stdin (requires a multiline command):

command << EOF <Enter> multiline_data <Enter> EOF

• Create a here string and pass that into stdin (achieves the same effect as echo string |):

command <<< string