Re: [ptxdist] git ptx-patches fails

[Michael Olbrich <m.olbrich@pengutronix.de>]

On Tue, Apr 01, 2014 at 11:59:42AM +0200, Alexander Stein wrote:
> Hello Uwe,
> 
> On Tuesday 01 April 2014 11:37:30, Uwe Kleine-König wrote:
> > On Tue, Apr 01, 2014 at 11:24:52AM +0200, Alexander Stein wrote:
> > > On Tuesday 01 April 2014 10:24:41, Uwe Kleine-König wrote:
> > > > On Mon, Mar 31, 2014 at 07:08:53PM +0200, Alexander Stein wrote:
> > > > > On Saturday 29 March 2014, 10:28:54 wrote Michael Olbrich:
> > > > > > On Thu, Mar 27, 2014 at 08:16:15AM +0100, Alexander Stein wrote:
> > > > > > > I tried to use git ptx-patches fromwithin a package and noticed it doesn't work.
> > > > > > > I could track down the problem to this command (from scripts/git-ptx-patches):
> > > > > > > > man git-format-patch | grep -q -e --notes
> > > > > > > 
> > > > > > > Executing this command manually results in this error message:
> > > > > > > > Error executing formatting or display command.
> > > > > > > > System command (cd "/usr/share/man" && (echo ".pl 11i"; /bin/bzip2 -c -d '/usr/share/man/man1/git-format-patch.1.bz2') | /usr/bin/gtbl | /usr/bin/nroff -mandoc | less) exited with status 141.
> > > > > > > > No manual entry for git-format-patch
> > > > > > > 
> > > > > > > Interestingly executing
> > > > > > > > (cd "/usr/share/man" && (echo ".pl 11i"; /bin/bzip2 -c -d '/usr/share/man/man1/git-format-patch.1.bz2') | /usr/bin/gtbl | /usr/bin/nroff -mandoc | less) | grep -q -e --notes
> > > > > > > works as expected. I have no idea what's wrong here.
> > > > > > 
> > > > > > Maybe this is caused by some aliases or interactive/non-ineractive magic.
> > > > > > Does it help to replace "man git-format-patch" with "git format-patch
> > > > > > --help" or "man -P cat git-format-patch"?
> > > > > 
> > > > > Unfortunately no :(
> > > > > 
> > > > > git format-patch --help | grep -q -e --notes
> > > > > Error executing formatting or display command.
> > > > > System command (cd "/usr/share/man" && (echo ".pl 11i"; /bin/bzip2 -c -d '/usr/share/man/man1/git-format-patch.1.bz2') | /usr/bin/gtbl | /usr/bin/nroff -mandoc | /usr/bin/less) exited with status 141.
> > > > > No manual entry for git-format-patch
> > > > > 
> > > > > $ man -P cat git-format-patch | grep -q -e --notes
> > > > > Error executing formatting or display command.
> > > > > System command (cd "/usr/share/man" && (echo ".pl 11i"; /bin/bzip2 -c -d '/usr/share/man/man1/git-format-patch.1.bz2') | /usr/bin/gtbl | /usr/bin/nroff -mandoc | cat) exited with status 141.
> > > > > No manual entry for git-format-patch
> > > > Do you have git-format-patch's manpage, i.e. does
> > > > 
> > > > 	man git-format-patch
> > > > 
> > > > work?
> > > 
> > > Yep, that man page is installed.
> > > 
> > > > On bash, what happens on:
> > > > 
> > > > 	$ man -P cat git-format-patch | grep -q -e --notes
> > > > 	$ echo ${PIPESTATUS[@]}
> > > 
> > > $ man -P cat git-format-patch | grep -q -e --notes
> > > Error executing formatting or display command.
> > > System command (cd "/usr/share/man" && (echo ".pl 11i"; /bin/bzip2 -c -d '/usr/share/man/man1/git-format-patch.1.bz2') | /usr/bin/gtbl | /usr/bin/nroff -mandoc | cat) exited with status 141.
> > > No manual entry for git-format-patch
> > > $ echo ${PIPESTATUS[@]}
> > > 1 0
> > > 
> > > > Does
> > > > 
> > > > 	strace -f -o /tmp/lala man -P cat git-format-patch | grep -q -e --notes
> > > > 
> > > > give any insights (e.g. where does the 141 come from?)
> > > 
> > > Somewhat. The 'culprit' is grep so far:
> > > $ man -P cat git-format-patch | grep -q -e --notes
> > > Error executing formatting or display command.
> > > System command (cd "/usr/share/man" && (echo ".pl 11i"; /bin/bzip2 -c -d '/usr/share/man/man1/git-format-patch.1.bz2') | /usr/bin/gtbl | /usr/bin/nroff -mandoc | cat) exited with status 141.
> > > No manual entry for git-format-patch
> > > $ man -P cat git-format-patch | grep -e --notes
> > >                           [--[no-]cover-letter] [--quiet] [--notes[=<ref>]]
> > >        --notes[=<ref>]
> > > 
> > > It seems grep slightly behaves differently when used with -q. It closes STDIN as soon as it detects the pattern.
> > > But the closed pipe results in an EPIPE returned from write(2) within cat which exits with an error.
> > My man (from the Debian package man-db 2.6.2-1) doesn't show this
> > behaviour. Is your version older or newer?
> 
> I don't think this is related to man (what's man-db BTW?) at all.
> I think the versions of cat and grep behave differently. I have installed
> grep-2.16 and coreutils-8.21 (current Gentoo stable versions).

This is caused by 'man':

$ (cd "/usr/share/man" && (echo ".pl 11i"; /bin/gunzip -c -d '/usr/share/man/man1/git-format-patch.1.gz') | /usr/bin/gtbl | /usr/bin/nroff -mandoc | cat) | grep -q -e --notes
$ echo ${PIPESTATUS[@]}
141 0

$ man git-format-patch | grep -q -e --notes
$ echo ${PIPESTATUS[@]}
0 0

Either man is executing something else here or it ignores the return value.
Maybe it doesn't start a pager if stdout is a pipe, because:
$ (cd "/usr/share/man" && (echo ".pl 11i"; /bin/gunzip -c -d '/usr/share/man/man1/git-format-patch.1.gz') | /usr/bin/gtbl | /usr/bin/nroff -mandoc) | grep -q -e --notes
$ echo ${PIPESTATUS[@]}
0 0

Michael

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