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Author image Steve Roscio


Term::Emit - Print with indentation, status, and closure


This document describes Term::Emit version 0.0.4


For a script like this:

    use Term::Emit qw/:all/;
    emit "System parameter updates";
      emit "CLOCK_UTC";

      emit "NTP Servers";

      emit "DNS Servers";

You get this output:

   System parameter updates...
     CLOCK_UTC................................................. [OK]
     NTP Servers............................................... [ERROR]
     DNS Servers............................................... [WARN]
   System parameter updates.................................... [DONE]


The Term::Emit package is used to print balanced and nested messages with a completion status. These messages indent easily within each other, autocomplete on scope exit, are easily parsed, may be bulleted, can be filtered, and even can show status in color.

For example, you write code like this:

    use Term::Emit qw/:all/;
    emit "Reconfiguring the grappolator";

It begins by printing:

    Reconfiguring the grappolator...

Then it does "whatchamacallit" and "something else". When these are complete it adds the rest of the line: a bunch of dots and the [DONE].

    Reconfiguring the grappolator............................... [DONE]

Your do_whatchamacallit() and do_something_else() subroutines may also emit what they're doing, and indicate success or failure or whatever, so you can get nice output like this:

    Reconfiguring the grappolator...
      Processing whatchamacallit................................ [WARN]
      Fibulating something else...
        Fibulation phase one.................................... [OK]
        Fibulation phase two.................................... [ERROR]
        Wrapup of fibulation.................................... [OK]
    Reconfiguring the grappolator............................... [DONE]

A series of examples will make Term::Emit easier to understand.


    use Term::Emit ':all';
    emit "Frobnicating the biffolator";
    sleep 1; # simulate the frobnication process

First this prints:

    Frobnicating the biffolator...

Then after the "frobnication" process is complete, the line is continued so it looks like this:

    Frobnicating the biffolator................................ [DONE]


In the above example, we end with a emit_done call to indicate that the thing we told about (Frobnicating the biffolator) is now done. We don't need to do the emit_done. It will be called automatically for us when the current scope is exited (for this example: when the program ends). So the code example could be just this:

    use Term::Emit ':all';
    emit "Frobnicating the biffolator";
    sleep 1; # simulate the frobnication process

and we'd get the same results.

Yeah, autocompletion may not seem so useful YET, but hang in there and you'll soon see how wonderful it is.

Completion Severity

There's many ways a task can complete. It can be simply DONE, or it can complete with an ERROR, or it can be OK, etc. These completion codes are called the severity codes. Term::Emit defines many different severity codes. The severity codes are borrowed from the UNIX syslog subsystem, plus a few from VMS and other sources. They should be familiar to you.

Severity codes also have an associated numerical value. This value is called the severity level. It's useful for comparing severities to eachother or filtering out severities you don't want to be bothered with.

Here are the severity codes and their severity values. Those on the same line are considered equal in severity:

    EMERG => 15,
    ALERT => 13,
    CRIT  => 11, FAIL => 11, FATAL => 11,
    ERROR => 9,
    WARN  => 7,
    NOTE  => 6,
    INFO  => 5, OK => 5,
    DEBUG => 4,
    NOTRY => 3,
    UNK   => 2,
    YES   => 1,
    NO    => 0,

You may make up your own severities if what you want is not listed. Please keep the length to 5 characters or less, otherwise the text may wrap. Any severity not listed is given the value 1.

To complete with a different severity, call emit_done with the severity code like this:

    emit_done "WARN";

emit_done returns with the severity value from the above table, otherwise it returns 1, unless there's an error in which case it returns false.

As a convienence, it's easier to use these functions which do the same thing, only simpler:

     Function          Equivalent                       Usual Meaning
    ----------      -----------------      -----------------------------------------------------
    emit_emerg      emit_done "EMERG";     syslog: Off the scale!
    emit_alert      emit_done "ALERT";     syslog: A major subsystem is unusable.
    emit_crit       emit_done "CRIT";      syslog: a critical subsystem is not working entirely.
    emit_fail       emit_done "FAIL";      Failure
    emit_fatal      emit_done "FATAL";     Fatal error
    emit_error      emit_done "ERROR";     syslog 'err': Bugs, bad data, files not found, ...
    emit_warn       emit_done "WARN";      syslog 'warning'
    emit_note       emit_done "NOTE";      syslog 'notice'
    emit_info       emit_done "INFO";      syslog 'info'
    emit_ok         emit_done "OK";        copacetic
    emit_debug      emit_done "DEBUG";     syslog: Really boring diagnostic output.
    emit_notry      emit_done "NOTRY";     Untried
    emit_unk        emit_done "UNK";       Unknown
    emit_yes        emit_done "YES";       Yes
    emit_no         emit_done "NO";        No

We'll change our simple example to give a FATAL completion:

    use Term::Emit ':all';
    emit "Frobnicating the biffolator";
    sleep 1; # simulate the frobnication process

Here's how it looks:

    Frobnicating the biffolator................................ [FATAL]

Severity Colors

A spiffy little feature of Term::Emit is that you can enable colorization of the severity codes. That means that the severity code inside the square brackets is printed in color, so it's easy to see. The standard ANSI color escape sequences are used to do the colorization.

Here's the colors:

    EMERG    bold red on black
    ALERT    bold magenta
    CRIT     bold red
    FAIL     bold red
    FATAL    bold red
    ERROR    red
    WARN     yellow (usually looks orange)
    NOTE     cyan
    INFO     green
    OK       bold green
    DEBUG    grey on yellow/orange
    NOTRY    black on grey
    UNK      bold white on grey
    DONE     default font color (unchanged)
    YES      green
    NO       red

To use colors, do this when you use Term::Emit:

    use Term::Emit ":all", {-color => 1};
    Term::Emit::setopts(-color => 1);

Run sample003.pl, included with this module, to see how it looks on your terminal.

Nested Messages

Nested calls to emit will automatically indent with eachother. You do this:

    use Term::Emit ":all";
    emit "Aaa";
    emit "Bbb";
    emit "Ccc";

and you'll get output like this:

        Ccc.......................... [DONE]
      Bbb............................ [DONE]
    Aaa.............................. [DONE]

Notice how "Bbb" is indented within the "Aaa" item, and that "Ccc" is within the "Bbb" item. Note too how the Bbb and Aaa items were repeated because their initial lines were interrupted by more-inner tasks.

You can control the indentation with the -step attribute, and you may turn off or alter the repeated text (Bbb and Aaa) as you wish.

Nesting Across Processes

If you write a Perl script that uses Term::Emit, and this script invokes other scripts that also use Term::Emit, some nice magic happens. The inner scripts become aware of the outer, and they "nest" their indentation levels appropriately. Pretty cool, eh?

Filtering-out Deeper Levels (Verbosity)

Often a script will have a verbosity option (-v usually), that allows a user to control how much output to see. Term::Emit makes this easy with the -maxdepth option.

Suppose your script has the verbose option in $opts{verbose}, where 0 means no output, 1 means some output, 2 means more output, etc. In your script, do this:

    Term::Emit::setopts(-maxdepth => $opts{verbose});

Then output will be filtered from nothing to full-on based on the verbosity setting.

...But Show Severe Messages

If you're using -maxdepth to filter messages, sometimes you still want to see a message regardless of the depth filtering - for example, a severe error. To set this, use the -showseverity option. All messages that have at least that severity value or higher will be shown, regardless of the depth filtering. Thus, a better filter would look like:

    Term::Emit::setopts(-maxdepth     => $opts{verbose},
                        -showseverity => 7);

See "Completion Severity" above for the severity numbers. Note that the severity is rolled up to the deepest message filtered by the -maxdepth setting; any -reason text is hooked to that level.

Closing with Different Text

Suppose you want the opening and closing messages to be different. Such as "Starting gompchomper" and "End of the gomp".

To do this, use the -closetext option, like this:

    emit {-closetext => "End of the gomp"}, "Starting gompchomper";

Now, instead of the start message being repeated at the end, you get custom end text.

A convienent shorthand notation for -closetext is to instead call emit with a pair of strings as an array reference, like this:

    emit ["Start text", "End text"];

Using the array reference notation is easier, and it will override the -closetext option if you use both. So don't use both.

Changing the 'close text' afterwards

*** TODO: Provide an easy way to do this! ***

OK, you got me! I didn't think of this case when I built this module.

It's not easy to do now, even with access to the base object. For now, I recommend you use -reason and give extra reason text. When I fix it, it'll probably take the form of setopts(-closetext => "blah") and emit_done {-closetext=>"blah"};

Closing with Different Severities, or... Why Autocompletion is Nice

So far our examples have been rather boring. They're not vey real-world. In a real script, you'll be doing various steps, checking status as you go, and bailing out with an error status on each failed check. It's only when you get to the bottom of all the steps that you know it's succeeded. Here's where emit becomes more useful:

    use Term::Emit qw/:all/, {-closestat => "ERROR"};
    emit "Juxquolating the garfibnotor";
        if !do_kibvoration();
        if !do_rumbalation();
    $fail_reason = do_major_cleanup();
    return emit_warn {-reason => $fail_reason}
         if $fail_reason;

In this example, we set -closestat to "ERROR". This means that if we exit scope without doing a emit_done() (or its equivalents), a emit_error() will automatically be called.

Next we do_kibvoration and do_runbalation (whatever these are!). If either fails, we simply return. Automatically then, the emit_error() will be called to close out the context.

In the third step, we do_major_cleanup(). If that fails, we explicitly close out with a warning (the emit_warn), and we pass some reason text.

If we get thru all three steps, we close out with an OK.

Output to Other File Handles

By default, Term::Emit writes its output to STDOUT (or whatever select() is set to). You can tell Term::Emit to use another file handle like this:

    use Term::Emit qw/:all/, {-fh => *LOG};
    Term::Emit::setopts(-fh => *LOG);

Individual "emit" lines may also take a file handle as the first argument, in a manner similar to a print statement:

    emit *LOG, "this", " and ", "that";

Note the required comma after the *LOG -- if it was a print you would omit the comma.

Output to Strings

If you give Term::Emit a scalar (string) reference instead of a file handle, then Term::Emit's output will be appended to this string.

For example:

    my $out = "";
    use Term::Emit qw/:all/, {-fh => \$out};
    Term::Emit::setopts(-fh => \$out);

Individual "emit" lines may also take a scalar reference as the first argument:

    emit \$out, "this ", " and ", "that";

Output Independence

Term::Emit separates output contexts by file handle. That means the indentation, autoclosure, bullet style, width, etc. for any output told to STDERR is independent of output told to STDOUT, and independent of output told to a string. All output to a string is lumped together into one context.

Return Status

Like print, the emit function returns a true value on success and false on failure. Failure can occur, for example, when attempting to emit to a closed filehandle.

To get the return status, you must assign into a scalar context, not a list context:

      my $stat;
      $stat = emit "Whatever";      # OK. This puts status into $stat
      ($stat) = emit "Whatever";    # NOT what it looks like!

In list context, the closure for emit is bound to the list variable's scope and autoclosure is disabled. Probably not what you wanted.

Message Bullets

You may preceed each message with a bullet. A bullet is usually a single character such as a dash or an asterix, but may be multiple characters. You probably want to include a space after each bullet, too.

You may have a different bullet for each nesting level. Levels deeper than the number of defined bulelts will use the last bullet.

Define bullets by passing an array reference of the bullet strings with -bullet. If you want the bullet to be the same for all levels, just pass the string. Here's some popular bullet definitions:

    -bullets => "* "
    -bullets => [" * ", " + ", " - ", "   "]

Here's an example with bullets turned on:

 * Loading system information...
 +   Defined IP interface information......................... [OK]
 +   Running IP interface information......................... [OK]
 +   Web proxy definitions.................................... [OK]
 +   NTP Servers.............................................. [OK]
 +   Timezone settings........................................ [OK]
 +   Internal clock UTC setting............................... [OK]
 +   sshd Revocation settings................................. [OK]
 * Loading system information................................. [OK]
 * Loading current CAS parameters............................. [OK]
 * RDA CAS Setup 8.10-2...
 +   Updating configuration...
 -     System parameter updates............................... [OK]
 -     Updating CAS parameter values...
         Updating default web page index...................... [OK]
 -     Updating CAS parameter values.......................... [OK]
 +   Updating configuration................................... [OK]
 +   Forced stopping web server............................... [OK]
 +   Restarting web server.................................... [OK]
 +   Loading crontab jobs...remcon............................ [OK]
 * RDA CAS Setup 8.10-2....................................... [DONE]

Mixing Term::Emit with print'ed Output

Internally, Term::Emit keeps track of the output cursor position. It only knows about what it has spewed to the screen (or logfile or string...). If you intermix print statements with your emit output, then things will likely get screwy. So, you'll need to tell Term::Emit where you've left the cursor. Do this by setting the -pos option:

    emit "Skrawning all xyzons";
    print "\nHey, look at me, I'm printed output!\n";
    Term::Emit::setopts (-pos => 0);  # Tell where we left the cursor


Nothing is exported by default. You'll want to do one of these:

    use Term::Emit qw/emit emit_done/;    # To get just these two functions
    use Term::Emit qw/:all/;              # To get all functions

Most of the time, you'll want the :all form.


Although an object-oriented interface exists for Term::Emit, it is uncommon to use it that way. The recommended interface is to use the class methods in a procedural fashion. Use emit() similar to how you would use print().


The following subsections list the methods available:


Internal base object accessor. Called with no arguments, it returns the Term::Emit object associated with the default output filehandle. When called with a filehandle, it returns the Term::Emit object associated with that filehandle.


Clones the current Term::Emit object and returns a new copy. Any given attributes override the cloned object. In most cases you will NOT need to clone Term::Emit objects yourself.


Constructor for a Term::Emit object. In most cases you will NOT need to create Term::Emit objects yourself.


Sets options on a Term::Emit object. For example to enable colored severities, or to set the indentation step size. Call it like this:

        Term::Emit::setopts(-fh    => *MYLOG,
                            -step  => 3,
                            -color => 1);

See "Options".


Use emit to emit a message similar to how you would use print.

Procedural call syntax:

    emit LIST
    emit *FH, LIST
    emit \$out, LIST
    emit {ATTRS}, LIST

Object-oriented call syntax:

    $tobj->emit (LIST)
    $tobj->emit (*FH, LIST)
    $tobj->emit (\$out, LIST)
    $tobj->emit ({ATTRS}, LIST)


Closes the current message level, re-printing the message if necessary, printing dot-dot trailers to get proper alignment, and the given completion severity.
















All these are convienence methods that call emit_done() with the indicated severity. For example, emit_fail() is equivalent to emit_done "FAIL". See "Completion Severity".


This is equivalent to emit_done, except that it does NOT print a wrapup line or a completion severity. It simply closes out the current level with no message.



Emits a progress indication, such as a percent or M/N or whatever you devise. In fact, this simply puts *any* string on the same line as the original message (for the current level).

Using emit_over will first backspace over a prior progress string (if any) to clear it, then it will write the progress string. The prior progress string could have been emitted by emit_over or emit_prog; it doesn't matter.

emit_prog does not backspace, it simply puts the string out there.

For example,

  use Term::Emit qw/:all/;
  emit "Varigating the shaft";
  emit_prog '10%...';
  emit_prog '20%...';

gives this output:

  Varigating the shaft...10%...20%...

Keep your progress string small! The string is treated as an indivisible entity and won't be split. If the progress string is too big to fit on the line, a new line will be started with the appropriate indentation.

With creativity, there's lots of progress indicator styles you could use. Percents, countdowns, spinners, etc. Look at sample005.pl included with this package. Here's some styles to get you thinking:

        Style       Example output
        -----       --------------
        N           3       (overwrites prior number)
        M/N         3/7     (overwrites prior numbers)
        percent     20%     (overwrites prior percent)
        dots        ....    (these just go on and on, one dot for every step)
        tics        .........:.........:...
                            (like dots above but put a colon every tenth)
        countdown   9... 8... 7...


This prints the given text without changing the current level. Use it to give additional information, such as a blob of description. Lengthy lines will be wrapped to fit nicely in the given width.


The emit* functions, the setopts() function, and use Term::Emit take the following optional attributes. Supply options and their values as a hash reference, like this:

    use Term::Emit ':all', {-fh => \$out,
                            -step => 1,
                            -color => 1};
    emit {-fh => *LOG}, "This and that";
    emit {-color => 1}, "Severities in living color";

The leading dash on the option name is optional, but encouraged; and the option name may be any letter case, but all lowercase is preferred.


Only valid for emit and emit_text. Supply an integer value.

This adjusts the indentation level of the message inwards (positive) or outwards (negative) for just this message. It does not affect filtering via the maxdepth attribute. But it does affect the bullet character(s) if bullets are enabled.


Enables or disables the use of bullet characters in front of messages. Set to a false value to disable the use of bullets - this is the default. Set to a scalar character string to enable that character(s) as the bullet. Set to an array reference of strings to use different characters for each nesting level. See "Message Bullets".


Sets the severity code to use when autocompleting a message. This is set to "DONE" by default. See "Closing with Different Severities, or... Why Autocompletion is Nice" above.


Valid only for emit.

Supply a string to be used as the closing text that's paired with this level. Normally, the text you use when you emit() a message is the text used to close it out. This option lets you specify different closing text. See "Closing with Different Text".


Set to a true value to render the completion severities in color. ANSI escape sequences are used for the colors. The default is to not use colors. See "Severity Colors" above.


Sets the string to use for the ellipsis at the end of a message. The default is "..." (three periods). Set it to a short string. This option is often used in combination with -trailer.

    Frobnicating the bellfrey...
                             ^^^_____ These dots are the ellipsis


May only be set before making the first emit() call.

Sets the base part of the environment variable used to maintain level-context across process calls. The default is "term_emit_". See "CONFIGURATION AND ENVIRONMENT".


Designates the filehandle or scalar to receive output. You may alter the default output, or specify it on individual emit* calls.

    use Term::Emit ':all', {-fh => *STDERR};  # Change default output to STDERR
    emit "Now this goes to STDERR instead of STDOUT";
    emit {-fh => *STDOUT}, "This goes to STDOUT";
    emit {-fh => \$outstr}, "This goes to a string";

The emit* methods have a shorthand notation for the filehandle. If the first argument is a filehandle or a scalar reference, it is presumed to be the -fh attribute. So the last two lines of the above example could be written like this:

    emit *STDOUT, "This goes to STDOUT";
    emit \$outstr, "This goes to a string";

The default filehandle is whatever was select()'ed, which is typically STDOUT.


Only valid with setopts() and use Term::Emit.

Filters messages by setting the maximum depth of messages tha will be printed. Set to undef (the default) to see all messages. Set to 0 to disable all messages from Term::Emit. Set to a positive integer to see only messages at that depth and less.


Used to reset what Term::Emit thinks the cursor position is. You may have to do this is you mix ordinary print statements with emit's.

Set this to 0 to indicate we're at the start of a new line (as in, just after a print "\n"). See "Mixing Term::Emit with print'ed Output".


Only valid for emit_done (and its equivalents like emit_warn, emit_error, etc.).

Causes emit_done() to emit the given reason string on the following line(s), indented underneath the completed message. This is useful to supply additional failure text to explain to a user why a certain task failed.

This programming metaphor is commonly used:

    my $fail_reason = do_something_that_may_fail();
    return emit_fail {-reason => $fail_reason}
        if $fail_reason;


Only valid for emit(), emit_done(), and it's equivalents, like emit_ok, emit_warn, etc.

Set this option to a true value to make an emit_done() close out silently. This means that the severity code, the trailer (dot dots), and the possible repeat of the message are turned off.

The return status from the call is will still be the appropriate value for the severity code.


Sets the indentation step size (number of spaces) for nesting messages. The default is 2. Set to 0 to disable indentation - all messages will be left justified. Set to a small positive integer to use that step size.


If false (the default), emitted lines are not prefixed with a timestamp. If true, the default local timestamp HH::MM::SS is prefixed to each emit line. If it's a coderef, then that function is called to get the timestamp string. The function is passed the current indent level, for what it's worth. Note that no delimiter is provided between the timestamp string and the emitted line, so you should provide your own (a space or colon or whatever). Also, emit_text() output is NOT timestamped, just that from emit() and its closure.


The single character used to trail after a message up to the completion severity. The default is the dot (the period, "."). Here's what messages look like if you change it to an underscore:

  The code:
    use Term::Emit ':all', {-trailer => '_'};
    emit "Xerikineting";

  The output:
    Xerikineting...______________________________ [DONE]

Note that the ellipsis after the message is still "..."; use -ellipsis to change that string as well.


Indicates the needed matching scope level for an autoclosure call to emit_done(). This is really an internal option and you should not use it. If you do, I'll bet your output would get all screwy. So don't use it.


Sets the terminal width of your output device. Term::Emit has no idea how wide your terminal screen is, so use this option to indicate the width. The default is 80.

You may want to use Term::Size::Any to determine your device's width:

    use Term::Emit ':all';
    use Term::Size::Any 'chars';
    my ($cols, $rows) = chars();
    Term::Emit::setopts(-width => $cols);


Term::Emit requires no configuration files or environment variables. However, it does set environment variables with this form of name:


This envvar holds the current level of messages (represented visually by indentation), so that indentation can be smoothly maintained across process contexts.

In this envvar's name, fd# is the fileno() of the output file handle to which the messages are written. By default output is to STDERR, which has a fileno of 2, so the envvar would be term_emit_fd2. If output is being written to a string (<-fh = \$some_string>>), then fd# is the string "str", for example term_emit_fdstr

When Term::Emit is used with threads, the thread ID is placed in th# in the envvar. Thus for thread #7, writing Term::Emit messages to STDERR, the envvar would be term_emit_fd2_th7. For the main thread, th# and the leading underscore are omitted.

Under normal operation, this environment variable is deleted before the program exits, so generally you won't see it.

Note: If your program's output seems excessively indented, it may be that this envvar has been left over from some other aborted run. Check for it and delete it if found.


This pure-Perl module depends upon Scope::Upper.




None reported.


Limitation: Output in a threaded environment isn't always pretty. It works OK and won't blow up, but indentation may get a bit screwy. I'm workin' on it.

Bugs: No bugs have been reported.

Please report any bugs or feature requests to bug-term-emit@rt.cpan.org, or through the web interface at http://rt.cpan.org.


To format Term::Emit output to HTML, use Term::Emit::Format::HTML .

Other modules like Term::Emit but not quite the same:


Steve Roscio <roscio@cpan.org>


Thanx to Paul Vencel for his review of this package, and to Jimmy Maguire for his namespace advice.


Copyright (c) 2009-2012, Steve Roscio <roscio@cpan.org>. All rights reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See perlartistic.


Because this software is licensed free of charge, there is no warranty for the software, to the extent permitted by applicable law. Except when otherwise stated in writing the copyright holders and/or other parties provide the software "as is" without warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose. The entire risk as to the quality and performance of the software is with you. Should the software prove defective, you assume the cost of all necessary servicing, repair, or correction.

In no event unless required by applicable law or agreed to in writing will any copyright holder, or any other party who may modify and/or redistribute the software as permitted by the above licence, be liable to you for damages, including any general, special, incidental, or consequential damages arising out of the use or inability to use the software (including but not limited to loss of data or data being rendered inaccurate or losses sustained by you or third parties or a failure of the software to operate with any other software), even if such holder or other party has been advised of the possibility of such damages.