The output of my program has a .raw file extension. If I try to open this with less I get:

No isoinfo available
Install mkisofs to view ISO images

The file isn't an image file, it's just text. Is there a way to tell less that the file should be opened as plain text?

  • 1
    try with strings command: strings file.raw|less Jun 7, 2015 at 16:43
  • If I really want to see what's in a file, I use more rather than less.
    – Mark
    Jun 8, 2015 at 7:10
  • 1
    To really see what's in a file, I use od ;-). Jun 8, 2015 at 9:45

2 Answers 2


The attempt to use isoinfo comes from lesspipe, which is generally used as a helper for less via the LESSOPEN variable.


LESSOPEN= less file.raw

will open file.raw without interpretation.


Another option which doesn't involve setting any variables is to pipe the data through less instead of letting less open the file for you.

$ cat file.raw | less


$ less <file.raw

would do the trick.

  • This is also great suggestion; if I could accept two answers I would also accept this. Jun 7, 2015 at 18:37
  • 3
    Using redirections into less has a couple of disadvantages: less needs to buffer everything, so it will use more memory (unless -B is specified); it won't know about the file name, and the size will only be available once it's finished reading all the data. Jun 8, 2015 at 8:59

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