For example, how can I replicate:
ls *.txt
when my text files are missing the .txt ending, and as far as extensions go appear the same as many other types of file?
Alternatively, is it possible to list specifically just the files which have NO file extension?
To match files that do not have an extension at all, you can use the command
ls | grep -v '\.'
To match files that do not have a .txt extension, you can use the command
ls | grep -v '\.txt'
This will pass the list of files in the current directory to grep, which will remove all file names that have a . (or .txt for the second command) in them.
grep can be used with any command. The | symbol is used to pass output from one command to another, and grep will match lines that have (or don't have) specific text. But if you want to modify the text (other than just printing matching lines), you should take a look at the sed command.
ls --classify | grep -v '/'.'*'
With ls -ignore="PATTERN" you can exclude files from a ls result.
For example, ls --ignore="*.txt" to ignore txt files.
Simply negate your pattern (note: shopt -s extglob is required).
To display all files without extension:
ls !(*.*)
To show non-txt files, try:
ls !(*.txt)
The command ls -SX1|less will sort by extension in a single column and files without one will be moved to the top. Piping through less as in the example is suggested for directories with more than a few files to limit output to a screen full at a time.
I prefer avoiding the use of grep for simple listing operations.
In order to avoid using grep,
I recommend using ls !(*.*) to find files with no file extension,
and
ls -I "*.gz" -I "*.tz" or ls --ignore={"*.jpg","*.png","*.bmp"}
to exclude specific file extensions
