Bug 91497

Summary: The "-n" in "echo -n foo > /sys/bar" is not posix and not needed
Product: pm-utils Reporter: Alexandre Rostovtsev <tetromino>
Component: GeneralAssignee: Richard Hughes <richard>
Status: RESOLVED WONTFIX QA Contact:
Severity: normal    
Priority: medium CC: fieldhouse, freedesktop-bugs
Version: unspecified   
Hardware: Other   
OS: All   
Whiteboard:
i915 platform: i915 features:
Attachments: proposed patch
patch based on review of patch 117432 taken from running pm-functions

Description Alexandre Rostovtsev 2015-07-29 02:23:38 UTC 
(reported downstream https://bugs.gentoo.org/show_bug.cgi?id=527848)

According to posix, the effect of the "-n" argument to echo is implementation-dependent. So a few shells, like the heavily patched variant of dash that Gentoo ships, do strange things with it - e.g. "echo -n foo" outputs "-n foo".

If such a shell is used as /bin/sh, the "echo -n mem /sys/power/state" calls in pm-utils will fail.

And that "-n" is not needed even when using bash: when writing to /sys/power/state, or almost anything else in /sys, the terminal newline doesn't make a difference.
Comment 1 Alexandre Rostovtsev 2015-07-29 02:28:53 UTC 
Created attachment 117432 [details] [review]
proposed patch
Comment 2 /df 2016-02-22 20:19:05 UTC 
Rather than changing all these, consider adding a shell function as follows:

echo()
{
	local fmt='%s\n'
	[ "$1" = "-n" ] && { fmt='%s'; shift; }
	printf "$fmt" "$*"
}

You can then redefine the existing log() function (line 90):

log()
{
	is_set "$LOGGING" || return 0;
	echo $*
}

This will (a) work on all platforms where log() now works (b) support use of "echo -n" in the code in case future contributors should introduce any.
Comment 3 /df 2016-02-28 01:27:24 UTC 
Created attachment 122011 [details]
patch based on review of patch 117432 taken from running pm-functions
Comment 4 Adam Jackson 2018-06-29 19:57:07 UTC 
pm-utils hasn't been touched in eight years, none of this is likely to get addressed. Closing bugs and disabling the bz product.

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