Setting Breakpoints and Continuing

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# 11.2. Setting Breakpoints and Continuing

When one places a breakpoint on a certain line in a program, he indicates that the execution of the program must be stopped when this line is reached. Then, one can cause the program to run freely using the continue command, and have it stop only at this line.

Breakpoints generally save a lot of stepping. To set a breakpoint type `b $line_number` or `b $function_name` where $line_number is the line number and $function_name is the function name. A breakpoint on a function will stop the execution of the program as soon as the function is entered.

To continue the execution of the program until a breakpoint is reached (or until the program terminates) type `c`. Here is an example session with the same program:

    shlomi:~/bin# perl -d add_cr.pl test.txt
    Default die handler restored.

    Loading DB routines from perl5db.pl version 1.07
    Editor support available.

    Enter h or `h h' for help, or `man perldebug' for more help.

    main::(add_cr.pl:5):	my ($contents);
      DB<1> b 11
      DB<2> c
    main::(add_cr.pl:11):	    open I, "<$file";
      DB<2>

One can set a conditional breakpoint by typing `b [line] [perl expression]`. A conditional expression is one that stops the execution of the program only if the perl expression evaluates to true. The perl expression can be as complex as you like and may include whitespace.

To delete a breakpoint type `d [line]`. After a breakpoint is deleted it will no longer affect the execution of your program.

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