Linux and Unix ul command
The ul utility performs the underlining of text.
ul [-i] [-t terminal] [file ...]
The ul utility reads the named files (or standard input if none are given) and translates occurrences of underscores to the sequence which indicates underlining for the terminal in use, as specified by the environment variable TERM. The file /etc/termcap is read to determine the appropriate sequences for underlining. If the terminal is incapable of underlining, but is capable of a standout mode (boldface, for example) then that is used instead. If the terminal can overstrike, or handles underlining automatically, ul degenerates to a level of operation equivalent to cat. If the terminal cannot underline, underlining is ignored. During the translation some other special characters also get translated; for example, tabs get expanded to spaces.
|-i||Underlining is indicated by a separate line containing appropriate dashes ‘-’; this is useful when you want to look at the underlining which is present in an nroff output stream on a terminal.|
|-t terminal||Overrides the terminal type specified in the environment with terminal type terminal.|
The LANG, LC_ALL, LC_CTYPE and TERM environment variables affect the execution of ul.
Processes myfile.txt for the underlining of text.