PERL -d参数用来debug的方法

sjtusonic

还在通过在代码加各种“if” "print"来调试脚本吗？这样已经落伍了，要像个牛人一样debug。

以下列出几条必备命令，帮助你轻松调试：


perl -d myprogram
Essentially the -d switch allows you to communicate with the perlexecutable, and allows the perl executable to communicate with you.
Stepping up to the plate

• l - lists the next few lines
• p [variable name] - lets you print the value of a variable to the              command line
• q - I quit.
• r - returns from current subroutine
  If you have written your program as a few subroutines, this is handy for running through each and checking the return.
           
• n - executes the next statement at this level
  Meansyou don't have to go through those boring subroutine calls. If youdon't know what I just wrote, get into a program and try it a couple oftimes. You'll get the hang of it.
              
• s - The step command
  Okay,this is the key for simple debugging. Crank up your program in thedebugger and step through it. If its a small program, this and the rcommand can take care of most of your needs. By the way, once you enterthe s command, just hit enter to repeat the command.
                 

            Breaking away
            Breakpointsallow you to specify the next stopping point in a program. For example,lets say I know my problems at line 65, I might insert a breakpoint atline 60 and step through the final five lines of code before theproblem. You just saved hitting the enter key 60 times.
            b - Set a breakpoint
            Once you have started the perl debugger you may set a breakpoint at any executable line number.
            b 20 - Sets a breakpoint at line 20.
            b subroutinename - handy little deviation.  If you know the subroutine name, this breaks on the first line inside the routine.
            b 20 condition- depending on your background, this is called a conditional breakpointor watchpoint. Perl breaks when the condition you specify is met.
            

Examples
• b 20 x>30 Breaks at line 20 when x is greater than 30
• b 20 x=~/foo/i Breaks at line 20 when x contains "foo"

            To start the program use c (continue), which runs the program to the first breakpoint or watchpoint.