sh is a symlink to bash but man sh shows man page of ksh

M0M0 · 02-23-2021, 08:24 AM

I just noticed that, wouldn't it make more sense to show the man page of bash instead?

pan64 · 02-23-2021, 09:36 AM

no, the shell (and other programs) may detect their invocation and behave accordingly. so sh and bash work differently.

M0M0 · 02-23-2021, 09:39 AM

ok, but sh does definitely not behave like ksh.

pan64 · 02-23-2021, 09:42 AM

see man bash

Quote:

If bash is invoked with the name sh, it tries to mimic the startup behavior of historical versions of sh as closely as possible, while conforming to the POSIX standard as well.

Yes, that is probably a misconfiguration of man pages.

ponce · 02-23-2021, 09:47 AM

I can replicate this on an updated machine, while on a fresh installed one (a couple of hours ago)

Code:

$ man sh
No manual entry for sh

bassmadrigal · 02-23-2021, 12:08 PM

Quote:

Originally Posted by ponce

I can replicate this on an updated machine, while on a fresh installed one (a couple of hours ago)

Code:

$ man sh
No manual entry for sh

I also don't have a man page for sh on my 14.2 install, but if I check on my htpc using an old version of -current (from around May 2019), that does bring up ksh's man page.

If I run man -w sh, it shows /usr/man/man1/ksh.1.gz

I'm not sure if that's a glitch with an older version of man or if there's something like a symlink that allows man to link to ksh when running it against sh.

drumz · 02-23-2021, 12:30 PM

Quote:

Originally Posted by bassmadrigal

I also don't have a man page for sh on my 14.2 install, but if I check on my htpc using an old version of -current (from around May 2019), that does bring up ksh's man page.

If I run man -w sh, it shows /usr/man/man1/ksh.1.gz

I'm not sure if that's a glitch with an older version of man or if there's something like a symlink that allows man to link to ksh when running it against sh.

I agree, on my 14.2 install:

Code:

$ man sh
No manual entry for sh

But on Pop!_OS 20.04 LTS (derivative of Ubuntu):

Code:

$ man -w sh
/usr/share/man/man1/dash.1.gz
$ find /usr/share/man -iname sh.*
/usr/share/man/man1/sh.1.gz
/usr/share/man/man1/sh.distrib.1.gz
$ ls -l /usr/share/man/man1/sh.1.gz 
lrwxrwxrwx 1 root root 9 Jul 18  2019 /usr/share/man/man1/sh.1.gz -> dash.1.gz
$ ls -l /usr/share/man/man1/sh.distrib.1.gz 
lrwxrwxrwx 1 root root 9 Jan 25  2018 /usr/share/man/man1/sh.distrib.1.gz -> dash.1.gz

So I'm guessing a symlink was created at some point on -current. Maybe try searching in /var/log/scripts and/or /var/log/removed_scripts/ ?

Petri Kaukasoina · 02-23-2021, 01:08 PM

The start of the ksh man page talks something about sh.

Code:

$ gzip -dc /usr/man/man1/ksh.1.gz |head -46
.\"
.\" David Korn
.\" AT&T Bell Laboratories
.\"
.\" @(#)sh.1 (dgk@research.att.com) 12/28/93
.\"
.nr Z 1 \" set to 1 when command name is ksh, 2 for ksh93
.ds OK [\|
.ds CK \|]
.ds ' \s+4\v@.3m@\'\v@-.3m@\s-4
.ds ` \s+4\v@.3m@\`\v@-.3m@\s-4
.if \nZ=0  \{\
.TH SH 1
.\}
.if \nZ=1 \{\
.TH KSH 1
.\}
.if \nZ=2 \{\
.TH KSH93 1
.\}
.SH NAME
.if \nZ=0 \{\
sh, rsh, pfsh \- shell, the standard/restricted command and programming language
.\}
.if \nZ=1 \{\
ksh, rksh, pfksh \- KornShell, a standard/restricted command and programming language
.\}
.SH NOTE
Currently,
.I rksh
and
.I pfksh
are not available on macOS / Darwin.
.if \nZ=2 \{\
ksh93, rksh93, pfksh93 \- KornShell, a standard/restricted command and programming language
.\}
.SH SYNOPSIS
.if \nZ=0 \{\
.B sh
.\}
.if \nZ=1 \{\
.B ksh
.\}
.if \nZ=2 \{\
.B ksh93
.\}

/usr/bin/mandb puts it in /var/cache/man/usr-man/index.db. There is a script /etc/cron.daily/man-db that cron runs at 4:40 every night.

bassmadrigal · 02-23-2021, 02:24 PM

Quote:

Originally Posted by drumz

I agree, on my 14.2 install:

Code:

$ man sh
No manual entry for sh

But on Pop!_OS 20.04 LTS (derivative of Ubuntu):

Code:

$ man -w sh
/usr/share/man/man1/dash.1.gz
$ find /usr/share/man -iname sh.*
/usr/share/man/man1/sh.1.gz
/usr/share/man/man1/sh.distrib.1.gz
$ ls -l /usr/share/man/man1/sh.1.gz 
lrwxrwxrwx 1 root root 9 Jul 18  2019 /usr/share/man/man1/sh.1.gz -> dash.1.gz
$ ls -l /usr/share/man/man1/sh.distrib.1.gz 
lrwxrwxrwx 1 root root 9 Jan 25  2018 /usr/share/man/man1/sh.distrib.1.gz -> dash.1.gz

So I'm guessing a symlink was created at some point on -current. Maybe try searching in /var/log/scripts and/or /var/log/removed_scripts/ ?

I did forget to mention that on my old -current system, there is no file or symlink for sh.1.gz, so I'm not sure how it links to ksh.1.gz when you run man -w sh

Petri Kaukasoina · 02-23-2021, 02:33 PM

Quote:

Originally Posted by bassmadrigal

I did forget to mention that on my old -current system, there is no file or symlink for sh.1.gz, so I'm not sure how it links to ksh.1.gz when you run man -w sh

Via /var/cache/man/usr-man/index.db

bassmadrigal · 02-23-2021, 02:45 PM

But if I don't have any sh.1.gz file or symlink, how did sh get mapped to ksh on my old -current? And why did 14.2 not have that happen and why does it not happen with a fresh install of -current?

I don't know a lot about man and how the index.db is created.

Petri Kaukasoina · 02-23-2021, 02:58 PM

Quote:

Originally Posted by bassmadrigal

But if I don't have any sh.1.gz file or symlink, how did sh get mapped to ksh on my old -current? And why did 14.2 not have that happen and why does it not happen with a fresh install of -current?

I don't know a lot about man and how the index.db is created.

See https://www.linuxquestions.org/quest...9/#post6223702
Your new -current has not been on at 4:40 yet?
Slackware 14.2 did not have man-db:

Code:

Wed Nov 29 08:15:09 UTC 2017
ap/man-1.6g-x86_64-3.txz:  Removed.
ap/man-db-2.7.6.1-x86_64-1.txz:  Added.
  This package replaces the good old man package. Thanks to B. Watson.

bassmadrigal · 02-23-2021, 03:30 PM

ponce is the one who stated that a new install didn't show the issue, but looking at the doinst.sh, it seems database creation is commented out, so it wouldn't happen until cron is run at 4:40.

So, since you simply linked your old post when I asked how it happened, I'm assuming man-db actually looks in the man pages to generate its index rather than just filenames? I didn't know how the database was created, which is why I asked. Looking in the bash.1.gz file, there's also mentions of sh, so I'm not sure what portions man-db looks at to generate its cache. It seems most distros just symlink sh.1.gz with the system's preferred shell (and maybe that's the best option here if ksh.1.gz maps itself to sh because of text inside the man file).

Petri Kaukasoina · 02-23-2021, 03:46 PM

Quote:

Originally Posted by bassmadrigal

So, since you simply linked your old post when I asked how it happened, I'm assuming man-db actually looks in the man pages to generate its index rather than just filenames? I didn't know how the database was created, which is why I asked.

Yes, I guess so. I think it's these two lines in my post:

Code:

.SH NAME
sh, rsh, pfsh \- shell, the standard/restricted command and programming language

Actually, it's inside an if Z=0, but it seems mandb does not take into account that Z=1. If it did, it would use this:

Code:

.SH NAME
ksh, rksh, pfksh \- KornShell, a standard/restricted command and programming language

("man pfsh" shows the man page, but "man pfksh" does not.)

bassmadrigal · 02-23-2021, 04:29 PM

Quote:

Originally Posted by Petri Kaukasoina

Yes, I guess so. I think it's these two lines in my post:

Code:

.SH NAME
sh, rsh, pfsh \- shell, the standard/restricted command and programming language

Actually, it's inside an if Z=0, but it seems mandb does not take into account that Z=1. If it did, it would use this:

That line seems to be the cause because man pfsh also shows ksh (an rsh man page actually exists and loads using man rsh, so it looks like man-db will prioritize files over one commands specified in a man page).

Seems like if we want man sh to show bash (since that is the default shell), the best option would be to simply create a symlink for /usr/man/man1/sh.1.gz pointing to /usr/man/man1/bash.1.gz