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I just tried to pass a search pattern starting with $ to less:

less +/'\$l' myfile.pl

and I got

There is no -l option ("less --help" for help)

After reading the manual, I tried the alternate -p-option

less -p'\$l' myfile.pl

and got the same error.

Then I found, that (n.b. the space after -p)

less -p '\$l' myfile.pl

works, i.e. opens the file without error message and jumps to first occurrence of $l.

The long option variant --pattern=$l does not work

less --pattern='\$l' myfile.pl
There is no -l option ("less --help" for help)

whereas space instead of = works

less --pattern '\$l' myfile.pl

This is 

less -V
less 458 (POSIX regular expressions)
Copyright (C) 1984-2012 Mark Nudelman

on openSUSE Leap 42.3

Now the question: is this a bug?

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2 Answers 2

Reset to default
1

From man less:

   --use-backslash
          This option changes the interpretations of options which  follow
          this one.  After the --use-backslash option, any backslash in an
          option string is removed and the following  character  is  taken
          literally.   This  allows a dollar sign to be included in option
          strings.

We then need to escape both the backslash and the dollar, so

less --use-backslash +'/\\\$l' myfile.pl
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0

That's caused by a feature. From man less:

Some options like -k or -D require a string to follow the option letter. The string for that option is considered to end when a dollar sign ($) is found. For example, you can set two -D options on MS-DOS like this:

LESS="Dn9.1$Ds4.1"

So you could do:

LESS='ppattern$i' PAGER=less man less

To start less, looking for pattern case-insensitively.

--use-backslash may be used to allow \ to escape that $.

Now, while it makes sense for the $LESS variable, it makes little sense for arguments to options on the command line. In that, it could be seen as a bug which you may want to report.

Also note that that $ processing only occurs when that $ occurs in the same argument as that containing the option which explains the discrepancy between your -p '\$l' vs -p'\$l' and --pattern '\$l' vs --pattern='\$l' causing confusion and more justification that it may be seen as a bug.

Note that you'll also have problems for:

less -p' foo'

Where less looks for "foo" instead of " foo" (again use -p ' foo' instead). Look at the scan_option() function in options.c in the source for details.

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2
  • but this does not really explain the different behaviour when called with a space or not for the short -p resp. space or = for --pattern Commented Apr 16, 2018 at 15:34
  • @mararm, see edit. Commented Apr 16, 2018 at 15:58

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