pager isn’t just less or moreSo I was creating a pager Go Bonzai branch package1 and named the binary pager and ran into something really odd. Suddenly, git diff was running my pager program and not diffing any more. At first I thought git had some pager magic going on (which it does) but it turns out that there is a /usr/bin/pager that actually exists. I can’t say how long its been in Linux, or if it is also a UNIX thing. But it seems pretty standard.
The man man page has this to say:
-P pager, --pager=pager
Specify which output pager to use. By default, man uses pager, falling
back to cat if pager is not found or is not executable. This option
overrides the $MANPAGER environment variable, which in turn overrides
the $PAGER environment variable. It is not used in conjunction with -f
or -k.
The value may be a simple command name or a command with arguments, and
may use shell quoting (backslashes, single quotes, or double quotes).
It may not use pipes to connect multiple commands; if you need that, use
a wrapper script, which may take the file to display either as an
argument or on standard input.
So it looks like this has been a part of UNIX from the beginning. The binary pager has always been used, even if $PAGER isn’t defined. This means naming anything pager is a big no-no unless you really are committed to taking over paging of everything on the system with your fancy, custom version2 (which I’m not).
$ type pager
pager is hashed (/home/rwxrob/.local/bin/pager)
$ which pager
/usr/bin/pager
$ exec bash -l
$ which pager
/usr/bin/pager
$ type pager
pager is /usr/bin/pager
$ pager -l
There is no -l option ("less --help" for help)
Missing filename ("less --help" for help)
$ ^Cger -l
$ ls -l `which pager`
lrwxrwxrwx 1 root root 23 Apr 20 2022 /usr/bin/pager -> /etc/alternatives/pager
$ ls -l /etc/alternatives/pager
lrwxrwxrwx 1 root root 13 Apr 20 2022 /etc/alternatives/pager -> /usr/bin/less
$ ls -l /usr/bin/less
-rwxr-xr-x 1 root root 195K Mar 24 2022 /usr/bin/less
$ man pager