.rn '' }`
-''' $Header: perl.man.1,v 1.0 87/12/18 16:18:16 root Exp $
+''' $Header: perl.man.1,v 1.0.1.2 88/01/30 17:04:07 root Exp $
'''
''' $Log: perl.man.1,v $
+''' Revision 1.0.1.2 88/01/30 17:04:07 root
+''' patch 11: random cleanup
+'''
+''' Revision 1.0.1.1 88/01/28 10:24:44 root
+''' patch8: added eval operator.
+'''
''' Revision 1.0 87/12/18 16:18:16 root
''' Initial revision
'''
compiles it to an internal form.
If the script is syntactically correct, it is executed.
.Sh "Options"
-Note: on first reading this section won't make much sense to you. It's here
+Note: on first reading this section may not make much sense to you. It's here
at the front for easy reference.
.PP
A single-character option may be combined with the following option, if any.
To suppress printing use the
.B \-n
switch.
+A
+.B \-p
+overrides a
+.B \-n
+switch.
.TP 5
.B \-P
causes your script to be run through the C preprocessor before
.TP 5
.B \-s
enables some rudimentary switch parsing for switches on the command line
-after the script name but before any filename arguments.
-Any switch found there will set the corresponding variable in the
+after the script name but before any filename arguments (or before a --).
+Any switch found there is removed from @ARGV and sets the corresponding variable in the
.I perl
script.
The following script prints \*(L"true\*(R" if and only if the script is
-invoked with a -x switch.
+invoked with a -xyz switch.
.nf
.ne 2
#!/bin/perl -s
- if ($x) { print "true\en"; }
+ if ($xyz) { print "true\en"; }
.fi
.Sh "Data Types and Objects"
print "The price is $Price.\e\|n";\h'|3.5i'# interpreted
.fi
+Note that you can put curly brackets around the identifier to delimit it
+from following alphanumerics.
.PP
Array literals are denoted by separating individual values by commas, and
enclosing the list in parentheses.
For example,
.nf
+.ne 4
@foo = ('cc', '\-E', $bar);
assigns the entire array value to array foo, but
The command is executed each time the pseudo-literal is evaluated.
Unlike in \f2csh\f1, no interpretation is done on the
data\*(--newlines remain newlines.
+The status value of the command is returned in $?.
.PP
Evaluating a filehandle in angle brackets yields the next line
from that file (newline included, so it's never false until EOF).
It also uses filehandle ARGV internally.
You can modify @ARGV before the first <> as long as you leave the first
filename at the beginning of the array.
+Line numbers ($.) continue as if the input was one big happy file.
.PP
+.ne 5
If you want to set @ARGV to you own list of files, go right ahead.
If you want to pass switches into your script, you can
put a loop on the front like this:
LABEL BLOCK continue BLOCK
.fi
-(Note that, unlike C and Pascal, these are defined in terms of BLOCKs, not
+Note that, unlike C and Pascal, these are defined in terms of BLOCKs, not
statements.
This means that the curly brackets are \fIrequired\fR\*(--no dangling statements allowed.
If you want to write conditionals without curly brackets there are several
die "Can't open $foo" unless open(foo);
open(foo) || die "Can't open $foo"; # foo or bust!
open(foo) ? die "Can't open $foo" : 'hi mom';
+ # a bit exotic, that last one
.fi
-though the last one is a bit exotic.)
.PP
The
.I if
(See the
.I do
operator below. Note also that the loop control commands described later will
-NOT work in this construct, since loop modifiers don't take loop labels.
+NOT work in this construct, since modifiers don't take loop labels.
Sorry.)
.Sh "Expressions"
Since
$cnt = (chown $uid,$gid,'foo');
.fi
+.ne 18
Here's an example of looking up non-numeric uids:
.nf
-.ne 16
print "User: ";
$user = <stdin>;
open(pass,'/etc/passwd') || die "Can't open passwd";
assigned produces a FALSE (0) value).
The next call to each() after that will start iterating again.
The iterator can be reset only by reading all the elements from the array.
+You should not modify the array while iterating over it.
The following prints out your environment like the printenv program, only
in a different order:
.nf
}
.fi
+.Ip "eval EXPR" 8 6
+EXPR is parsed and executed as if it were a little perl program.
+It is executed in the context of the current perl program, so that
+any variable settings, subroutine or format definitions remain afterwards.
+The value returned is the value of the last expression evaluated, just
+as with subroutines.
+If there is a syntax error or runtime error, a null string is returned by
+eval, and $@ is set to the error message.
+If there was no error, $@ is null.
.Ip "exec LIST" 8 6
If there is more than one argument in LIST,
calls execvp() with the arguments in LIST.
''' Beginning of part 2
-''' $Header: perl.man.2,v 1.0 87/12/18 16:18:41 root Exp $
+''' $Header: perl.man.2,v 1.0.1.2 88/01/30 17:04:28 root Exp $
'''
''' $Log: perl.man.2,v $
+''' Revision 1.0.1.2 88/01/30 17:04:28 root
+''' patch 11: random cleanup
+'''
+''' Revision 1.0.1.1 88/01/28 10:25:11 root
+''' patch8: added $@ variable.
+'''
''' Revision 1.0 87/12/18 16:18:41 root
''' Initial revision
'''
with a \*(L"|\*(R", the filename is interpreted as command which pipes
input to us.
(You may not have a command that pipes both in and out.)
-On non-pipe opens, the filename '\-' represents either stdin or stdout, as
-appropriate.
+Opening '\-' opens stdin and opening '>\-' opens stdout.
Open returns 1 upon success, '' otherwise.
Examples:
.nf
Shifts the first value of the array off, shortening the array by 1 and
moving everything down.
If ARRAY is omitted, shifts the ARGV array.
-See also unshift().
+See also unshift(), push() and pop().
+Shift() and unshift() do the same thing to the left end of an array that push()
+and pop() do to the right end.
.Ip "sleep EXPR" 8 6
.Ip "sleep" 8
Causes the script to sleep for EXPR seconds, or forever if no EXPR.
(Note that the delimiter may be longer than one character.)
Trailing null fields are stripped, which potential users of pop() would
do well to remember.
-A pattern matching the null string will split into separate characters.
+A pattern matching the null string will split the value of EXPR into separate
+characters.
.sp
Example:
.nf
Does exactly the same thing as \*(L"exec LIST\*(R" except that a fork
is done first, and the parent process waits for the child process to complete.
Note that argument processing varies depending on the number of arguments.
+The return value is the exit status of the program.
See exec.
.Ip "tell(FILEHANDLE)" 8 6
.Ip "tell" 8
$cnt = (unlink 'a','b','c');
.fi
+.ne 7
.Ip "unshift(ARRAY,LIST)" 8 4
Does the opposite of a shift.
Prepends list to the front of the array, and returns the number of elements
The value should be copied elsewhere before any pattern matching happens, which
clobbers $0.
(Mnemonic: same as sh and ksh.)
+.Ip $<digit> 8
+Contains the subpattern from the corresponding set of parentheses in the last
+pattern matched, not counting patterns matched in nested blocks that have
+been exited already.
+(Mnemonic: like \edigit.)
.Ip $[ 8 2
The index of the first element in an array, and of the first character in
a substring.
.Ip $! 8 2
The current value of errno, with all the usual caveats.
(Mnemonic: What just went bang?)
+.Ip $@ 8 2
+The error message from the last eval command.
+If null, the last eval parsed and executed correctly.
+(Mnemonic: Where was the syntax error "at"?)
.Ip @ARGV 8 3
The array ARGV contains the command line arguments intended for the script.
Note that $#ARGV is the generally number of arguments minus one, since
a2p awk to perl translator
.br
s2p sed to perl translator
+.br
+perldb interactive perl debugger
.SH DIAGNOSTICS
Compilation errors will tell you the line number of the error, with an
indication of the next token or token type that was to be examined.
projects / platform / upstream / perl.git / commitdiff