Perl Introduction (10) formatted output

perl Use format Define output templates , Use write Output by template .

1、format Format

format You need to define the format name , Format line , Data line and end symbol “.”, The format is as follows ：

format FormatName = #  Define format name 
fieldline #  Format line , Used to define the format of an output line , similar  @,^,<,>,|  Such characters .
value_one, value_two, value_three #  data row , Used to insert values into the previous format line , All are perl The variable of .
fieldline
value_one, value_two
.

Examples are as follows ：

#!/usr/bin/perl

$text = "google it taobao";
format STDOUT =
first: ^<<<<<  #  Align left , The character length is 6
    $text
second: ^<<<<< #  Align left , The character length is 6
    $text
third: ^<<<< #  Align left , The character length is 5,taobao  the last one  o  Truncated 
    $text  
.
write

The operation results are as follows ：

$perl main.pl
first: google  #  Align left , The character length is 6
second: it     #  Align left , The character length is 6
third: taoba #  Align left , The character length is 5,taobao  the last one  o  Truncated 

2、 Format line

Format lines are in @ perhaps ^ start , Define only the format, not the variables .

@ Field ( Don't use array symbols @ To confuse ) It's a normal field .

@,^ After <, >,| The length determines the length of the field , If the variable exceeds the defined length , Then it will be truncated .

<, >,| It also means , Align left , Right alignment , Align center .

^ Fields are used for multi line text block filling .

Examples are as follows :

#!/usr/bin/perl

format EMPLOYEE =
===================================
@<<<<<<<<<<<<<<<<<<<<<< @<< 
$name, $age
@#####.##
$salary
===================================
.
select(STDOUT);
$~ = EMPLOYEE;
@n = ("Ali", "it", "Jaffer");
@a  = (20,30, 40);
@s = (2000.00, 2500.00, 4000.000);
$i = 0;
foreach (@n){
    $name = $_;
    $age = $a[$i];
    $salary = $s[$i++]; ## $i++ It means after execution $i add 1
    write;
}

The operation results are as follows ：

$perl main.pl
===================================
Ali                     20
  2000.00
===================================
===================================
it                      30
  2500.00
===================================
===================================
Jaffer                  40
  4000.00
===================================

3、 Format variable

$~ ($FORMAT_NAME) ： Format name

$^ ($FORMAT_TOP_NAME) ： Header format name

$% ($FORMAT_PAGE_NUMBER) ： Page number

$= ($FORMAT_LINES_PER_PAGE)： Number of lines per page

$| ($FORMAT_AUTOFLUSH) ： Whether to automatically refresh the output buffer storage

Examples are as follows ：

#!/usr/bin/perl

format EMPLOYEE =
===================================
@<<<<<<<<<<<<<<<<<<<<<< @##.##         
$name, $age
@#####.##                              ##  Format line , Use integer 5 position , decimal 2 Bit output format 
$salary
===================================
.                                      ##  Terminator .
#  Add pagination  $% 
format EMPLOYEE_TOP =
===================================
Name                    Age Page @<    ##  Format line , Align left 
$%                                     ##  data row , Output page number 
=================================== 
.

$~ = EMPLOYEE;                         ##  Use format EMPLOYEE Make reports                              
$^ = EMPLOYEE_TOP;                     ##  Use format EMPLOYEE_TOP Make the header 
@n = ("Ali", "it", "Jaffer");
@a  = (20,30, 40);
@s = (2000.00, 2500.00, 4000.000);
$i = 0;
foreach (@n){
   $name = $_;
   $age = $a[$i];
   $salary = $s[$i++];
   write;
}

The operation results are as follows ：

$perl main.pl
===================================
Name                    Age Page 1 
===================================
===================================
Ali                     20
  2000.00
===================================
===================================
it                      30
  2500.00
===================================
===================================
Jaffer                  40
  4000.00
===================================

4、 Output to other files

By default, functions write Output the results to the standard output file STDOUT, We can also make it output the results to any other file . The simplest way is to pass file variables as parameters to write, Such as ：

write(MYFILE);

Use select Specify a filename ,write You don't need to choose a file name later .

Examples are as follows ：

#!/usr/bin/perl
if (open(MYFILE, ">>tmp")) {
select (MYFILE); #  Print out the default file variables to MYFILE in 
$~ = "OTHER";
write;           #  Default file variables , print to select In the specified file , Must use $~ Specified format  OTHER
format OTHER =
=================================
   Use the defined format to input into the file 
=================================
. 
close MYFILE;
}

The operation results are as follows ：

$ cat tmp 
=================================
       Import into file 
=================================
=================================
   Use the defined format to input into the file 
=================================

If not used select, that format The format name of the file needs to be the same as the file name . The above example should be changed to ：

#!/usr/bin/perl
if (open(MYFILE, ">>tmp")) {
$~ = "OTHER";                  ##  there $~ It doesn't work , because write File variable name of MYFILE And 
                               ## format The format name of is the same  
write（MYFILE）;           
format MYFILE =
=================================
   Use the defined format to input into the file 
=================================
. 
close MYFILE;
}