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Edmund J. Sutcliffe
Thoughtful Solutions, Creatively Implemented and Communicated
Edmund's Perl Quick Reference -
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Formats
- formline
PICTURE, LIST
- Formats LIST according to PICTURE and accumulates
the result into $^A.
- write [ FILEHANDLE ]
- Writes a formatted record to the specified
file, using the format associated with that file.
Formats are defined as follows:
format [NAME] =
FORMLIST
.
FORMLIST pictures the lines, and contains the arguments which
will give values to the fields in the lines. NAME defaults
to STDOUT if omitted.
Picture fields are:
| @<<<... |
left adjusted field, repeat the <
to denote the desired width |
| @>>>... |
right adjusted field |
| @|||... |
centered field |
| @#.##... |
numeric format with implied decimal point |
| @* |
a multi-line field |
Use ^ instead of @
for multiline block filling.
Use ~ at the beginning of a line to suppress
unwanted empty lines.
Use ~~ at the beginning of a line to have this
format line repeated until all fields are exhausted.
Use $- to zero to force a page break on the
next write.
See also $^, $~, $^A,
$^F, $- and $=
Directory Reading Routines
- closedir
DIRHANDLE
- Closes a directory opened by opendir.
- opendir DIRHANDLE, DIRNAME
- Opens a directory on the handle specified.
- readdir DIRHANDLE
- Returns the next entry (or an array of entries)
from the directory.
- rewinddir DIRHANDLE
- Positions the directory to the beginning.
- seekdir DIRHANDLE, POS
- Sets position for readdir on the directory.
- telldir DIRHANDLE
- Returns the position in the directory.
System Interaction
- alarm
EXPR
- Schedules a SIGALRM to be delivered
after EXPR seconds.
- chdir [ EXPR ]
- Changes the working directory. Uses $ENV{"HOME"}
or $ENV{"LOGNAME"} if EXPR is omitted.
- chroot FILENAME†
- Changes the root directory for the process
and its children.
- die [ LIST ]
- Prints the value of LIST to STDERR
and exits with the current value of $! (errno).
If $! is 0, exits with the value of ($?
>> 8). If ($? >> 8)
is 0, exits with 255. LIST defaults to "Died".
- exec LIST
- Executes the system command in LIST; does not
return.
- exit EXPR
- Exits immediately with the value of EXPR, which
defaults to 0 (zero). Calls END
routines and object destructors before exiting.
- fork
- Does a fork(2) system call. Returns
the process ID of the child to the parent process and zero
to the child process.
- getlogin
- Returns the current login name as known by
the system.
- getpgrp [ PID ]
- Returns the process group for process PID (0,
or omitted, means the current process).
- getppid
- Returns the process ID of the parent process.
- getpriority WHICH, WHO
- Returns the current priority for a process,
process group, or user.
- glob PAT
- Returns a list of filenames that match the
shell pattern PAT.
- kill LIST
- Sends a signal to a list of processes. The
first element of the list must be the signal to send (either
numeric, or its name as a string).
- setpgrp PID, PGRP
- Sets the process group for the PID (0 means
the current process).
- setpriority WHICH, WHO,
PRIORITY
- Sets the current priority for a process, process
group, or a user.
- sleep [ EXPR ]
- Causes the program to sleep for EXPR seconds,
or forever if no EXPR. Returns the number of seconds actually
slept.
- syscall LIST
- Calls the system call specified in the first
element of the list, passing the rest of the list as arguments
to the call.
- system LIST
- Does exactly the same thing as exec
LIST except that a fork is performed first, and the parent
process waits for the child process to complete.
- times
- Returns a 4-element array (0: $user,
1: $system, 2: $cursor,
3: $csystem) giving the user and system
times, in seconds, for this process and the children of
this process.
- umask [ EXPR ]
- Sets the umask for the process and returns
the old one. If EXPR is omitted, returns current umask value.
- wait
- Waits for a child process to terminate and
returns the process ID of the deceased process (-1 if none).
The status is returned in $?.
- waitpid PID, FLAGS
- Performs the same function as the corresponding
system call.
- warn [ LIST ]
- Prints the message on STDERR
like die, but doesn't exit. LIST defaults to "Warning:
something's wrong".
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