second--glance appear to be an lvalue context may be fixed in a future
release.
-See L<perlref/"Pseudo-hashes: Using an array as a hash"> for specifics
-on how exists() acts when used on a pseudo-hash.
-
Use of a subroutine call, rather than a subroutine name, as an argument
to exists() is an error.
Returns the process id of the parent process.
+Note for Linux users: on Linux, the C functions C<getpid()> and
+C<getppid()> return different values from different threads. In order to
+be portable, this behavior is not reflected by the perl-level function
+C<getppid()>, that returns a consistent value across threads. If you want
+to call the underlying C<getppid()>, consider using C<Inline::C> or
+another way to call a C library function.
+
=item getpriority WHICH,WHO
Returns the current priority for a process, a process group, or a user.
$name = getpwuid($num);
$name = getpwent();
$gid = getgrnam($name);
- $name = getgrgid($num;
+ $name = getgrgid($num);
$name = getgrent();
#etc.
Returns a random fractional number greater than or equal to C<0> and less
than the value of EXPR. (EXPR should be positive.) If EXPR is
-omitted, or a C<0>, the value C<1> is used. Automatically calls C<srand>
-unless C<srand> has already been called. See also C<srand>.
+omitted, the value C<1> is used. Currently EXPR with the value C<0> is
+also special-cased as C<1> - this has not been documented before perl 5.8.0
+and is subject to change in future versions of perl. Automatically calls
+C<srand> unless C<srand> has already been called. See also C<srand>.
Apply C<int()> to the value returned by C<rand()> if you want random
integers instead of random fractional numbers. For example,
limited control of the sort. Its rather blunt control of the
underlying algorithm may not persist into future perls, but the
ability to characterize the input or output in implementation
-independent ways quite probably will. See L</use>.
+independent ways quite probably will. See L<sort>.
Examples:
%O a synonym for %lo
%F a synonym for %f
-Note that the number of exponent digits in the scientific notation by
-C<%e>, C<%E>, C<%g> and C<%G> for numbers with the modulus of the
+Note that the number of exponent digits in the scientific notation produced
+by C<%e>, C<%E>, C<%g> and C<%G> for numbers with the modulus of the
exponent less than 100 is system-dependent: it may be three or less
(zero-padded as necessary). In other words, 1.23 times ten to the
99th may be either "1.23e99" or "1.23e099".
-Perl permits the following universally-known flags between the C<%>
-and the conversion letter:
+Between the C<%> and the format letter, you may specify a number of
+additional attributes controlling the interpretation of the format.
+In order, these are:
+
+=over 4
+
+=item format parameter index
+
+An explicit format parameter index, such as C<2$>. By default sprintf
+will format the next unused argument in the list, but this allows you
+to take the arguments out of order. Eg:
+
+ printf '%2$d %1$d', 12, 34; # prints "34 12"
+ printf '%3$d %d %1$d', 1, 2, 3; # prints "3 1 1"
+=item flags
+
+one or more of:
space prefix positive number with a space
+ prefix positive number with a plus sign
- left-justify within the field
0 use zeros, not spaces, to right-justify
- # prefix non-zero octal with "0", non-zero hex with "0x"
- number minimum field width
- .number "precision": digits after decimal point for
- floating-point, max length for string, minimum length
- for integer
- l interpret integer as C type "long" or "unsigned long"
- h interpret integer as C type "short" or "unsigned short"
- If no flags, interpret integer as C type "int" or "unsigned"
-
-Perl supports parameter ordering, in other words, fetching the
-parameters in some explicitly specified "random" ordering as opposed
-to the default implicit sequential ordering. The syntax is, instead
-of the C<%> and C<*>, to use C<%>I<digits>C<$> and C<*>I<digits>C<$>,
-where the I<digits> is the wanted index, from one upwards. For example:
-
- printf "%2\$d %1\$d\n", 12, 34; # will print "34 12\n"
- printf "%*2\$d\n", 12, 3; # will print " 12\n"
-
-Note that using the reordering syntax does not interfere with the usual
-implicit sequential fetching of the parameters:
-
- printf "%2\$d %d\n", 12, 34; # will print "34 12\n"
- printf "%2\$d %d %d\n", 12, 34; # will print "34 12 34\n"
- printf "%3\$d %d %d\n", 12, 34, 56; # will print "56 12 34\n"
- printf "%2\$*3\$d %d\n", 12, 34, 3; # will print " 34 12\n"
- printf "%*3\$2\$d %d\n", 12, 34, 3; # will print " 34 12\n"
-
-There are also two Perl-specific flags:
-
- V interpret integer as Perl's standard integer type
- v interpret string as a vector of integers, output as
- numbers separated either by dots, or by an arbitrary
- string received from the argument list when the flag
- is preceded by "*"
-
-Where a number would appear in the flags, an asterisk (C<*>) may be
-used instead, in which case Perl uses the next item in the parameter
-list as the given number (that is, as the field width or precision).
+ # prefix non-zero octal with "0", non-zero hex with "0x",
+ non-zero binary with "0b"
+
+For example:
+
+ printf '<% d>', 12; # prints "< 12>"
+ printf '<%+d>', 12; # prints "<+12>"
+ printf '<%6s>', 12; # prints "< 12>"
+ printf '<%-6s>', 12; # prints "<12 >"
+ printf '<%06s>', 12; # prints "<000012>"
+ printf '<%#x>', 12; # prints "<0xc>"
+
+=item vector flag
+
+The vector flag C<v>, optionally specifying the join string to use.
+This flag tells perl to interpret the supplied string as a vector
+of integers, one for each character in the string, separated by
+a given string (a dot C<.> by default). This can be useful for
+displaying ordinal values of characters in arbitrary strings:
+
+ printf "version is v%vd\n", $^V; # Perl's version
+
+Put an asterisk C<*> before the C<v> to override the string to
+use to separate the numbers:
+
+ printf "address is %*vX\n", ":", $addr; # IPv6 address
+ printf "bits are %0*v8b\n", " ", $bits; # random bitstring
+
+You can also explicitly specify the argument number to use for
+the join string using eg C<*2$v>:
+
+ printf '%*4$vX %*4$vX %*4$vX', @addr[1..3], ":"; # 3 IPv6 addresses
+
+=item (minimum) width
+
+Arguments are usually formatted to be only as wide as required to
+display the given value. You can override the width by putting
+a number here, or get the width from the next argument (with C<*>)
+or from a specified argument (with eg C<*2$>):
+
+ printf '<%s>', "a"; # prints "<a>"
+ printf '<%6s>', "a"; # prints "< a>"
+ printf '<%*s>', 6, "a"; # prints "< a>"
+ printf '<%*2$s>', "a", 6; # prints "< a>"
+ printf '<%2s>', "long"; # prints "<long>" (does not truncate)
+
If a field width obtained through C<*> is negative, it has the same
effect as the C<-> flag: left-justification.
-The C<v> flag is useful for displaying ordinal values of characters
-in arbitrary strings:
+=item precision, or maximum width
+
+You can specify a precision (for numeric conversions) or a maximum
+width (for string conversions) by specifying a C<.> followed by a number.
+For floating point formats, this specifies the number of decimal places
+to show (the default being 6), eg:
+
+ # these examples are subject to system-specific variation
+ printf '<%f>', 1; # prints "<1.000000>"
+ printf '<%.1f>', 1; # prints "<1.0>"
+ printf '<%.0f>', 1; # prints "<1>"
+ printf '<%e>', 10; # prints "<1.000000e+01>"
+ printf '<%.1e>', 10; # prints "<1.0e+01>"
+
+For integer conversions, specifying a precision implies that the
+output of the number itself should be zero-padded to this width:
- printf "version is v%vd\n", $^V; # Perl's version
- printf "address is %*vX\n", ":", $addr; # IPv6 address
- printf "bits are %*vb\n", " ", $bits; # random bitstring
+ printf '<%.6x>', 1; # prints "<000001>"
+ printf '<%#.6x>', 1; # prints "<0x000001>"
+ printf '<%-10.6x>', 1; # prints "<000001 >"
+
+For string conversions, specifying a precision truncates the string
+to fit in the specified width:
+
+ printf '<%.5s>', "truncated"; # prints "<trunc>"
+ printf '<%10.5s>', "truncated"; # prints "< trunc>"
+
+You can also get the precision from the next argument using C<.*>:
+
+ printf '<%.6x>', 1; # prints "<000001>"
+ printf '<%.*x>', 6, 1; # prints "<000001>"
+
+You cannot currently get the precision from a specified number,
+but it is intended that this will be possible in the future using
+eg C<.*2$>:
+
+ printf '<%.*2$x>', 1, 6; # INVALID, but in future will print "<000001>"
+
+=item size
+
+For numeric conversions, you can specify the size to interpret the
+number as using C<l>, C<h>, C<V>, C<q>, C<L> or C<ll>. For integer
+conversions, numbers are usually assumed to be whatever the default
+integer size is on your platform (usually 32 or 64 bits), but you
+can override this to use instead one of the standard C types, as
+supported by the compiler used to build Perl:
+
+ l interpret integer as C type "long" or "unsigned long"
+ h interpret integer as C type "short" or "unsigned short"
+ q, L or ll interpret integer as C type "long long" or "unsigned long long"
+ (if your platform supports such a type, else it is an error)
+
+For floating point conversions, numbers are usually assumed to be
+the default floating point size on your platform (double or long double),
+but you can force 'long double' with C<q>, C<L> or C<ll> if your
+platform supports them.
+
+The size specifier 'V' has no effect for Perl code, but it supported
+for compatibility with XS code; it means 'use the standard size for
+a Perl integer (or floating-point number)', which is already the
+default for Perl code.
+
+=item order of arguments
+
+Normally, sprintf takes the next unused argument as the value to
+format for each format specification. If the format specification
+uses C<*> to require additional arguments, these are consumed from
+the argument list in the order in which they appear in the format
+specification I<before> the value to format. Where an argument is
+specified using an explicit index, this does not affect the normal
+order for the arguments (even when the explicitly specified index
+would have been the next argument in any case).
+
+So:
+
+ printf '<%*.*s>', $a, $b, $c;
+
+would use C<$a> for the width, C<$b> for the precision and C<$c>
+as the value to format, while:
+
+ print '<%*1$.*s>', $a, $b;
+
+would use C<$a> for the width and the precision, and C<$b> as the
+value to format.
+
+Here are some more examples - beware that when using an explicit
+index, the C<$> may need to be escaped:
+
+ printf "%2\$d %d\n", 12, 34; # will print "34 12\n"
+ printf "%2\$d %d %d\n", 12, 34; # will print "34 12 34\n"
+ printf "%3\$d %d %d\n", 12, 34, 56; # will print "56 12 34\n"
+ printf "%2\$*3\$d %d\n", 12, 34, 3; # will print " 34 12\n"
+
+=back
If C<use locale> is in effect, the character used for the decimal
point in formatted real numbers is affected by the LC_NUMERIC locale.
7 size total size of file, in bytes
8 atime last access time in seconds since the epoch
9 mtime last modify time in seconds since the epoch
- 10 ctime inode change time (NOT creation time!) in seconds since the epoch
+ 10 ctime inode change time in seconds since the epoch (*)
11 blksize preferred block size for file system I/O
12 blocks actual number of blocks allocated
(The epoch was at 00:00 January 1, 1970 GMT.)
+(*) The ctime field is non-portable, in particular you cannot expect
+it to be a "creation time", see L<perlport/"Files and Filesystems">
+for details.
+
If stat is passed the special filehandle consisting of an underline, no
stat is done, but the current contents of the stat structure from the
last stat or filetest are returned. Example:
projects / p5sagit/p5-mst-13.2.git / blobdiff