->spew() not usable for procfs/sysfs virtual filesystems / readonly directories

[kentfredric]

This is because the directory cannot have nodes added to it, but the nodes are still writeable.

perl -MCarp::Always -MPath::Tiny=path -E 'path(q[/sys/devices/system/cpu/intel_pstate/max_perf_pct])->spew(100)'                                                                                                       
#Error sysopen on '/sys/devices/system/cpu/intel_pstate/max_perf_pct0831895': #Permission denied at /usr/lib64/perl5/vendor_perl/5.18.2/Path/Tiny.pm line 773.
#        Path::Tiny::Error::throw('Path::Tiny::Error', 'sysopen', '/sys/devices/system/cpu/intel_pstate/max_perf_pct0831895', 'Permission denied') called at /usr/lib64/perl5/vendor_perl/5.18.2/Path/Tiny.pm line 96
#        Path::Tiny::_throw('Path::Tiny=ARRAY(0x1602588)', 'sysopen') called at /usr/lib64/perl5/vendor_perl/5.18.2/Path/Tiny.pm line 376
#        Path::Tiny::filehandle('Path::Tiny=ARRAY(0x1602588)', 'HASH(0x15ef0e8)', '>', undef) called at /usr/lib64/perl5/vendor_perl/5.18.2/Path/Tiny.pm line 696
#        Path::Tiny::spew('Path::Tiny=ARRAY(0x1602498)', 100) called at -e line 1
echo 100 > /sys/devices/system/cpu/intel_pstate/max_perf_pct
echo $?
#0

The same is the case with files that are writable in directories that are not:

ls -lah
# total 204K
# drwxr-xr-x  2 root root 4.0K Apr  4 03:15 .
# drwxrwxrwt 20 root root 196K Apr  4 03:15 ..
# -rw-r--r--  1 kent kent    0 Apr  4 03:15 bar
perl -MPath::Tiny -E'path(q[./bar])->spew(q[hello])' 
# Error sysopen on 'bar8321321244076350': Permission denied at -e line 1.
echo world > bar
echo $?
#0
cat bar
# world

[dagolden]

That's by design and documented. Without that, an atomic write can't be guaranteed. If you need to write to such a file, you have to do it the old fashioned way and open a handle.

[kentfredric]

IME this is a candidate for an option for being unsafe / fast.

Just where you'd put it in the command is the question..

spew( $opthash?, @data );
...
spew( { direct => 1 }, @data ); 

or something.