思考反省每一天

#!/usr/bin/perl -wuse strict;# two ways to print meta-char# qq: qq can be followed by any symbol pairs, such as: //,||,{}print "$ @  ";pri

leave a tap

select($file); $|=1;# for now, write to file without buffered. issue:printing something to STDOUT will write in file instead of display of STDOUT.

The following topics will be covered. Exit value;system & exec - block the present process & swith to a new process, wait for them to finish before returning to next.capture output

1. work on $_ by default i.e. it will work on $_ if we dont give any vars;while ({                print if m/leo/;                print s/leo/LEO/;  # print number of matches foun

#!/opt/VRTSperl/bin/perl -wuse strict;my $file = shift;print "==================read file line by line/n";read_file("$/", $file);print "==================read the whole file at one time/n";

 #!/usr/bin/perl -wuse strict;my @arr = `cat /etc/llthosts | awk {print /$2}`;  #perl中使用shell命令，注意，$应该转义，否则perl会将$2解释为一个变量

1.考虑一个字符串替换的过程，在一个文本文件中含有一些文本内容和一些需要替换的变量，变量的格式为“$Var$”，原来的“$”使用“$$”进行转义，原来的“$$”表示为“$$$”。我们将含有变量的文件称为模板(文件名为t)，文本文件的平均长度为100K。另外，还有一系列的变量文件，里面为变量名和变量值的对应关系(文件名为1.v , 2.v…n.v)，每个变量文件包含的变量数在百万数量

1.  /^[a-z]+/d+$/begin with one or more lower chars [a-z], end with one or more digital numbers. 2. /^([a-z]+(/d)+)+$/the pattern above is repeated more than once.

#!/usr/bin/perl -wuse strict;=headthis section describe hash;=cut=head11 define: my %[a-zA-Z_]str; the name begin with a-zA-Z_, digit is denied; pair

#!/usr/bin/perl -wuse strict;=head11 condition:  false when value is 0/null string/string with "0" value/undef;2 block:  {}; vars only take effect in the block they are defined;3 c

#!/usr/bin/perl -wuse strict;=head11 condition:  false when value is 0/null string/string with "0" value/undef;2 block:  ...{}; vars only take effect in the block they are defined;3 compare operator

#!/usr/bin/perl -wuse strict;=head  this section describes file system;=cut=head11 test operators  2 built-in subroutines  chdir "directory" or die "$!"; chdir; ===