File: gawk.info,  Node: Viewing And Changing Data,  Next: Execution Stack,  Prev: Debugger Execution Control,  Up: List of Debugger Commands

14.3.3 Viewing and Changing Data
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The commands for viewing and changing variables inside of 'gawk' are:

'display' [VAR | '$'N]
     Add variable VAR (or field '$N') to the display list.  The value of
     the variable or field is displayed each time the program stops.
     Each variable added to the list is identified by a unique number:

          gawk> display x
          -| 10: x = 1

     This displays the assigned item number, the variable name, and its
     current value.  If the display variable refers to a function
     parameter, it is silently deleted from the list as soon as the
     execution reaches a context where no such variable of the given
     name exists.  Without argument, 'display' displays the current
     values of items on the list.

'eval "AWK STATEMENTS"'
     Evaluate AWK STATEMENTS in the context of the running program.  You
     can do anything that an 'awk' program would do: assign values to
     variables, call functions, and so on.

          NOTE: You cannot use 'eval' to execute a statement containing
          any of the following: 'exit', 'getline', 'next', 'nextfile',
          or 'return'.

'eval' PARAM, ...
AWK STATEMENTS
'end'
     This form of 'eval' is similar, but it allows you to define "local
     variables" that exist in the context of the AWK STATEMENTS, instead
     of using variables or function parameters defined by the program.

'print' VAR1[',' VAR2 ...]
'p' VAR1[',' VAR2 ...]
     Print the value of a 'gawk' variable or field.  Fields must be
     referenced by constants:

          gawk> print $3

     This prints the third field in the input record (if the specified
     field does not exist, it prints 'Null field').  A variable can be
     an array element, with the subscripts being constant string values.
     To print the contents of an array, prefix the name of the array
     with the '@' symbol:

          gawk> print @a

     This prints the indices and the corresponding values for all
     elements in the array 'a'.

'printf' FORMAT [',' ARG ...]
     Print formatted text.  The FORMAT may include escape sequences,
     such as '\n' (*note Escape Sequences::).  No newline is printed
     unless one is specified.

'set' VAR'='VALUE
     Assign a constant (number or string) value to an 'awk' variable or
     field.  String values must be enclosed between double quotes
     ('"'...'"').

     You can also set special 'awk' variables, such as 'FS', 'NF', 'NR',
     and so on.

'watch' VAR | '$'N ['"EXPRESSION"']
'w' VAR | '$'N ['"EXPRESSION"']
     Add variable VAR (or field '$N') to the watch list.  The debugger
     then stops whenever the value of the variable or field changes.
     Each watched item is assigned a number that can be used to delete
     it from the watch list using the 'unwatch' command.

     With a watchpoint, you may also supply a condition.  This is an
     'awk' expression (enclosed in double quotes) that the debugger
     evaluates whenever the watchpoint is reached.  If the condition is
     true, then the debugger stops execution and prompts for a command.
     Otherwise, 'gawk' continues executing the program.

'undisplay' [N]
     Remove item number N (or all items, if no argument) from the
     automatic display list.

'unwatch' [N]
     Remove item number N (or all items, if no argument) from the watch
     list.