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Full Discussion: Perl - backticks v system in if statements
Top Forums Shell Programming and Scripting Perl - backticks v system in if statements Post 79438 by gjkeenan on Wednesday 27th of July 2005 11:52:43 PM
Old 07-28-2005
Perl - backticks v system in if statements
Can someone explain the difference between backticks and system when
evaluated in these if statements:


sub getDate {
print "start date\n";
if ( system("/bin/date") ) {
print "can't get date\n";
exit(2);
}
print "finish date\n";
}

Returns the following:

start date
Thu Jul 28 12:13:59 EST 2005
finish date



While this:

sub getDate {
print "start date\n";
if ( `/bin/date` ) {
print "can't get date\n";
exit(2);
}
print "finish date\n";
}

Returns this:

start date
can't get date


Also - I'm not sure I understand the logic of the top if statement. If system() runs OK shouldn't the next two lines of the if statement then run i.e. the print and the exit?
gjkeenan
 

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LEARN ABOUT REDHAT

set_color

set_color(1)							       fish							      set_color(1)

NAME

       set_color - set_color - set the terminal color

set_color - set the terminal color
   Synopsis
       set_color [-v --version] [-h --help] [-b --background COLOR] [COLOR]

   Description
       Change the foreground and/or background color of the terminal. COLOR is one of black, red, green, brown, yellow, blue, magenta, purple,
       cyan, white and normal.

       o -b, --background Set the background color

       o -c, --print-colors Prints a list of all valid color names

       o -h, --help Display help message and exit

       o -o, --bold Set bold or extra bright mode

       o -u, --underline Set underlined mode

       o -v, --version Display version and exit

       Calling set_color normal will set the terminal color to whatever is the default color of the terminal.

       Some terminals use the --bold escape sequence to switch to a brighter color set. On such terminals, set_color white will result in a grey
       font color, while set_color --bold white will result in a white font color.

       Not all terminal emulators support all these features. This is not a bug in set_color but a missing feature in the terminal emulator.

       set_color uses the terminfo database to look up how to change terminal colors on whatever terminal is in use. Some systems have old and
       incomplete terminfo databases, and may lack color information for terminals that support it. Download and install the latest version of
       ncurses and recompile fish against it in order to fix this issue.

Version 1.23.1							  Sun Jan 8 2012						      set_color(1)
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