gawk: Viewing And Changing Data
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1 14.3.3 Viewing and Changing Data
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1 The commands for viewing and changing variables inside of 'gawk' are:
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1 'display' [VAR | '$'N]
1 Add variable VAR (or field '$N') to the display list. The value of
1 the variable or field is displayed each time the program stops.
1 Each variable added to the list is identified by a unique number:
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1 gawk> display x
1 -| 10: x = 1
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1 This displays the assigned item number, the variable name, and its
1 current value. If the display variable refers to a function
1 parameter, it is silently deleted from the list as soon as the
1 execution reaches a context where no such variable of the given
1 name exists. Without argument, 'display' displays the current
1 values of items on the list.
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1 'eval "AWK STATEMENTS"'
1 Evaluate AWK STATEMENTS in the context of the running program. You
1 can do anything that an 'awk' program would do: assign values to
1 variables, call functions, and so on.
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1 'eval' PARAM, ...
1 AWK STATEMENTS
1 'end'
1 This form of 'eval' is similar, but it allows you to define "local
1 variables" that exist in the context of the AWK STATEMENTS, instead
1 of using variables or function parameters defined by the program.
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1 'print' VAR1[',' VAR2 ...]
1 'p' VAR1[',' VAR2 ...]
1 Print the value of a 'gawk' variable or field. Fields must be
1 referenced by constants:
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1 gawk> print $3
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1 This prints the third field in the input record (if the specified
1 field does not exist, it prints 'Null field'). A variable can be
1 an array element, with the subscripts being constant string values.
1 To print the contents of an array, prefix the name of the array
1 with the '@' symbol:
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1 gawk> print @a
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1 This prints the indices and the corresponding values for all
1 elements in the array 'a'.
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1 'printf' FORMAT [',' ARG ...]
1 Print formatted text. The FORMAT may include escape sequences,
1 such as '\n' (⇒Escape Sequences). No newline is printed
1 unless one is specified.
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1 'set' VAR'='VALUE
1 Assign a constant (number or string) value to an 'awk' variable or
1 field. String values must be enclosed between double quotes
1 ('"'...'"').
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1 You can also set special 'awk' variables, such as 'FS', 'NF', 'NR',
1 and so on.
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1 'watch' VAR | '$'N ['"EXPRESSION"']
1 'w' VAR | '$'N ['"EXPRESSION"']
1 Add variable VAR (or field '$N') to the watch list. The debugger
1 then stops whenever the value of the variable or field changes.
1 Each watched item is assigned a number that can be used to delete
1 it from the watch list using the 'unwatch' command.
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1 With a watchpoint, you may also supply a condition. This is an
1 'awk' expression (enclosed in double quotes) that the debugger
1 evaluates whenever the watchpoint is reached. If the condition is
1 true, then the debugger stops execution and prompts for a command.
1 Otherwise, 'gawk' continues executing the program.
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1 'undisplay' [N]
1 Remove item number N (or all items, if no argument) from the
1 automatic display list.
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1 'unwatch' [N]
1 Remove item number N (or all items, if no argument) from the watch
1 list.
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