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Full Discussion: Perl : How is file handling working here??
Top Forums Shell Programming and Scripting Perl : How is file handling working here?? Post 302831881 by balajesuri on Friday 12th of July 2013 06:19:17 AM
Old 07-12-2013
Everytime you do read from a filehandle and store it in a scalar variable, then one line of input is read. (By one line, I mean the data until the next record separator).

Here is how it works internally:
When you open a filehandle, lets say, there's a mark that is at the beginning of file. The first time $rec = scalar <$INF> is encountered, the first line from file is read and referred by $rec. Now, the mark that we spoke of earlier, is at the character just after newline character (assuming newline as the default record separator). Now again when $rec = scalar <$INF> is encountered, one more line of data is read.

In the example code you provided in your post, a wrapper routine "readfile" reads one line of data and prints it.

The usual way of reading a file is to use a loop. Then again, that depends on what you really want to do:

Code:
open FH, "< /path/to/file";
while ($rec = <FH>) {
    print $rec;
}
close FH;

 

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LEARN ABOUT FREEBSD

mixer

MIXER(8)						    BSD System Manager's Manual 						  MIXER(8)

NAME

     mixer -- set/display soundcard mixer values

SYNOPSIS

     mixer [-f device] [-s | -S] [dev [[+|-]lvol[:[+|-]rvol]]] ...
     mixer [-f device] [-s | -S] recsrc ...
     mixer [-f device] [-s | -S] {^|+|-|=}rec rdev ...

DESCRIPTION

     The mixer utility is used to set and display soundcard mixer device levels.  It may also be used to start and stop recording from the sound-
     card.  The list of mixer devices that may be modified are:

	   vol, bass, treble, synth, pcm, speaker, line, mic, cd, mix, pcm2, rec, igain, ogain, line1, line2, line3, dig1, dig2, dig3, phin,
	   phout, video, radio, and monitor.

     Not all mixer devices are available.

     Without any arguments, mixer displays the current settings for all supported devices, followed by information about the current recording
     input devices.  If the dev argument is specified, mixer displays only the value for that dev.

     To modify the mixer value dev, the optional left and right channel settings of lvol[:rvol] may be specified.  The lvol and rvol arguments may
     be from 0 - 100.  Omitting dev and including only the channel settings will change the main volume level.

     If the left or right channel settings are prefixed with + or -, the value following will be used as a relative adjustment, modifying the cur-
     rent settings by the amount specified.

     If the -s flag is used, the current mixer values will be displayed in a format suitable for use as the command-line arguments to a future
     invocation of mixer (as above).

     The -S flag provides the above output without mixing field separators.

     To change the recording device you use one of:

	   ^rec  toggles rdev of possible recording devices

	   +rec  adds rdev to possible recording devices

	   -rec  removes rdev from possible recording devices

	   =rec  sets the recording device to rdev

     The above commands work on an internal mask.  After all the options have been parsed, it will set then read the mask from the sound card.
     This will let you see EXACTLY what the soundcard is using for the recording device(s).

     The option recsrc will display the current recording devices.

     The option -f device will open device as the mixer device.

FILES

     /dev/mixer  the default mixer device

SEE ALSO

     cdcontrol(1), sound(4)

HISTORY

     The mixer utility first appeared in FreeBSD 2.0.5.

AUTHORS

     Original source by Craig Metz <cmetz@thor.tjhsst.edu> and Hannu Savolainen.  Mostly rewritten by John-Mark Gurney <jmg@FreeBSD.org>.  This
     manual page was written by Mike Pritchard <mpp@FreeBSD.org>.

BSD
								   June 2, 2014 							       BSD
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