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perldoc -f -t and perldoc -t -f don't do the same thing #897
I used perldoc -f -t to get help on a function, instead of the
correct perldoc -t -f. Although it is strictly correct that
the form I used was strictly not correct, the output was garbage
as opposed to something sensible. It looks as if the output is
always the same, but I haven't tested that. Here's the output
of `perldoc -f -t sub': (108 lines of output delimited by +++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
=item I<-X> FILEHANDLE
=item I<-X> EXPR
=item I<-X>
A file test, where X is one of the letters listed below. This unary
operator takes one argument, either a filename or a filehandle, and
tests the associated file to see if something is true about it. If the
argument is omitted, tests C<$_>, except for C<-t>, which tests STDIN.
Unless otherwise documented, it returns C<1> for TRUE and C<''> for FALSE, or
the undefined value if the file doesn't exist. Despite the funny
names, precedence is the same as any other named unary operator, and
the argument may be parenthesized like any other unary operator. The
operator may be any of:
X<-r>X<-w>X<-x>X<-o>X<-R>X<-W>X<-X>X<-O>X<-e>X<-z>X<-s>X<-f>X<-d>X<-l>X<-p>
X<-S>X<-b>X<-c>X<-t>X<-u>X<-g>X<-k>X<-T>X<-B>X<-M>X<-A>X<-C>
-r File is readable by effective uid/gid.
-w File is writable by effective uid/gid.
-x File is executable by effective uid/gid.
-o File is owned by effective uid.
-R File is readable by real uid/gid.
-W File is writable by real uid/gid.
-X File is executable by real uid/gid.
-O File is owned by real uid.
-e File exists.
-z File has zero size.
-s File has nonzero size (returns size).
-f File is a plain file.
-d File is a directory.
-l File is a symbolic link.
-p File is a named pipe (FIFO), or Filehandle is a pipe.
-S File is a socket.
-b File is a block special file.
-c File is a character special file.
-t Filehandle is opened to a tty.
-u File has setuid bit set.
-g File has setgid bit set.
-k File has sticky bit set.
-T File is a text file.
-B File is a binary file (opposite of -T).
-M Age of file in days when script started.
-A Same for access time.
-C Same for inode change time.
Example:
while (<>) {
chop;
next unless -f $_; # ignore specials
#...
}
The interpretation of the file permission operators C<-r>, C<-R>,
C<-w>, C<-W>, C<-x>, and C<-X> is by default based solely on the mode
of the file and the uids and gids of the user. There may be other
reasons you can't actually read, write, or execute the file. Such
reasons may be for example network filesystem access controls, ACLs
(access control lists), read-only filesystems, and unrecognized
executable formats.
Also note that, for the superuser on the local filesystems, the C<-r>,
C<-R>, C<-w>, and C<-W> tests always return 1, and C<-x> and C<-X> return 1
if any execute bit is set in the mode. Scripts run by the superuser
may thus need to do a stat() to determine the actual mode of the file,
or temporarily set their effective uid to something else.
Note that C<-s/a/b/> does not do a negated substitution. Saying
C<-exp($foo)> still works as expected, however--only single letters
following a minus are interpreted as file tests.
The C<-T> and C<-B> switches work as follows. The first block or so of the
file is examined for odd characters such as strange control codes or
characters with the high bit set. If too many strange characters (E<gt>30%)
are found, it's a C<-B> file, otherwise it's a C<-T> file. Also, any file
containing null in the first block is considered a binary file. If C<-T>
or C<-B> is used on a filehandle, the current stdio buffer is examined
rather than the first block. Both C<-T> and C<-B> return TRUE on a null
file, or a file at EOF when testing a filehandle. Because you have to
read a file to do the C<-T> test, on most occasions you want to use a C<-f>
against the file first, as in C<next unless -f $file && -T $file>.
If any of the file tests (or either the C<stat()> or C<lstat()> operators) are given
the special filehandle consisting of a solitary underline, then the stat
structure of the previous file test (or stat operator) is used, saving
a system call. (This doesn't work with C<-t>, and you need to remember
that lstat() and C<-l> will leave values in the stat structure for the
symbolic link, not the real file.) Example:
print "Can do.\n" if -r $a || -w _ || -x _;
stat($filename);
print "Readable\n" if -r _;
print "Writable\n" if -w _;
print "Executable\n" if -x _;
print "Setuid\n" if -u _;
print "Setgid\n" if -g _;
print "Sticky\n" if -k _;
print "Text\n" if -T _;
print "Binary\n" if -B _;
I used perldoc -f -t to get help on a function, instead of the
correct perldoc -t -f. Although it is strictly correct that
the form I used was strictly not correct, the output was garbage
as opposed to something sensible.
perldoc -f foo delivers the description of the foo function.
You asked for perldoc -f -t.
You got the description of the Perl's `-t' function.
I used perldoc -f -t to get help on a function, instead of the
correct perldoc -t -f. Although it is strictly correct that
the form I used was strictly not correct, the output was garbage
as opposed to something sensible.
perldoc -f foo delivers the description of the foo function.
You asked for perldoc -f -t.
You got the description of the Perl's `-t' function.
Er, I thought -t was an operator, not a function.
But hey, I'm happy if you are.
G . W . Haywood <ged@C2H5OH.jubileegroup.co.uk> writes:
This is a bug report for perl from ged@jubileegroup.co.uk,
generated with the help of perlbug 1.26 running under perl 5.00503.
-----------------------------------------------------------------
[Please enter your report here]
I used perldoc -f -t to get help on a function, instead of the
correct perldoc -t -f. Although it is strictly correct that
the form I used was strictly not correct, the output was garbage
as opposed to something sensible.
It is not "garbage" - it is the documentation that relates to the '-t'
"function" which is what you (unitentionally) asked for ...
t looks as if the output is
always the same, but I haven't tested that. Here's the output
of `perldoc -f -t sub': (108 lines of output delimited by +++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
=item I<-X> FILEHANDLE
Activity
p5pRT commentedon Nov 26, 1999
From ged@C2H5OH.jubileegroup.co.uk
I used perldoc -f -t to get help on a function, instead of the
correct perldoc -t -f. Although it is strictly correct that
the form I used was strictly not correct, the output was garbage
as opposed to something sensible. It looks as if the output is
always the same, but I haven't tested that. Here's the output
of `perldoc -f -t sub': (108 lines of output delimited by +++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
=item I<-X> FILEHANDLE
=item I<-X> EXPR
=item I<-X>
A file test, where X is one of the letters listed below. This unary
operator takes one argument, either a filename or a filehandle, and
tests the associated file to see if something is true about it. If the
argument is omitted, tests C<$_>, except for C<-t>, which tests STDIN.
Unless otherwise documented, it returns C<1> for TRUE and C<''> for FALSE, or
the undefined value if the file doesn't exist. Despite the funny
names, precedence is the same as any other named unary operator, and
the argument may be parenthesized like any other unary operator. The
operator may be any of:
X<-r>X<-w>X<-x>X<-o>X<-R>X<-W>X<-X>X<-O>X<-e>X<-z>X<-s>X<-f>X<-d>X<-l>X<-p>
X<-S>X<-b>X<-c>X<-t>X<-u>X<-g>X<-k>X<-T>X<-B>X<-M>X<-A>X<-C>
-r File is readable by effective uid/gid.
-w File is writable by effective uid/gid.
-x File is executable by effective uid/gid.
-o File is owned by effective uid.
-R File is readable by real uid/gid.
-W File is writable by real uid/gid.
-X File is executable by real uid/gid.
-O File is owned by real uid.
-e File exists.
-z File has zero size.
-s File has nonzero size (returns size).
-f File is a plain file.
-d File is a directory.
-l File is a symbolic link.
-p File is a named pipe (FIFO), or Filehandle is a pipe.
-S File is a socket.
-b File is a block special file.
-c File is a character special file.
-t Filehandle is opened to a tty.
-u File has setuid bit set.
-g File has setgid bit set.
-k File has sticky bit set.
-T File is a text file.
-B File is a binary file (opposite of -T).
-M Age of file in days when script started.
-A Same for access time.
-C Same for inode change time.
Example:
while (<>) {
chop;
next unless -f $_; # ignore specials
#...
}
The interpretation of the file permission operators C<-r>, C<-R>,
C<-w>, C<-W>, C<-x>, and C<-X> is by default based solely on the mode
of the file and the uids and gids of the user. There may be other
reasons you can't actually read, write, or execute the file. Such
reasons may be for example network filesystem access controls, ACLs
(access control lists), read-only filesystems, and unrecognized
executable formats.
Also note that, for the superuser on the local filesystems, the C<-r>,
C<-R>, C<-w>, and C<-W> tests always return 1, and C<-x> and C<-X> return 1
if any execute bit is set in the mode. Scripts run by the superuser
may thus need to do a stat() to determine the actual mode of the file,
or temporarily set their effective uid to something else.
Note that C<-s/a/b/> does not do a negated substitution. Saying
C<-exp($foo)> still works as expected, however--only single letters
following a minus are interpreted as file tests.
The C<-T> and C<-B> switches work as follows. The first block or so of the
file is examined for odd characters such as strange control codes or
characters with the high bit set. If too many strange characters (E<gt>30%)
are found, it's a C<-B> file, otherwise it's a C<-T> file. Also, any file
containing null in the first block is considered a binary file. If C<-T>
or C<-B> is used on a filehandle, the current stdio buffer is examined
rather than the first block. Both C<-T> and C<-B> return TRUE on a null
file, or a file at EOF when testing a filehandle. Because you have to
read a file to do the C<-T> test, on most occasions you want to use a C<-f>
against the file first, as in C<next unless -f $file && -T $file>.
If any of the file tests (or either the C<stat()> or C<lstat()> operators) are given
the special filehandle consisting of a solitary underline, then the stat
structure of the previous file test (or stat operator) is used, saving
a system call. (This doesn't work with C<-t>, and you need to remember
that lstat() and C<-l> will leave values in the stat structure for the
symbolic link, not the real file.) Example:
print "Can do.\n" if -r $a || -w _ || -x _;
stat($filename);
print "Readable\n" if -r _;
print "Writable\n" if -w _;
print "Executable\n" if -x _;
print "Setuid\n" if -u _;
print "Setgid\n" if -g _;
print "Sticky\n" if -k _;
print "Text\n" if -T _;
print "Binary\n" if -B _;
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Perl Info
p5pRT commentedon Nov 26, 1999
From @mjdominus
perldoc -f foo delivers the description of the foo function.
You asked for perldoc -f -t.
You got the description of the Perl's `-t' function.
p5pRT commentedon Nov 26, 1999
From [Unknown Contact. See original ticket]
Hi there,
On Fri, 26 Nov 1999, Mark-Jason Dominus wrote:
Er, I thought -t was an operator, not a function.
But hey, I'm happy if you are.
Kind regards,
Ged Haywood.
p5pRT commentedon Nov 27, 1999
From [Unknown Contact. See original ticket]
G . W . Haywood <ged@C2H5OH.jubileegroup.co.uk> writes:
It is not "garbage" - it is the documentation that relates to the '-t'
"function" which is what you (unitentionally) asked for ...
--
Nick Ing-Simmons