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Contents → REFERENCE MANUAL → Syntax Description → Flow Control → For Statement

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The for statement comes in two forms. The first is

for ( expression1 ; expression2 ; expression3 ) statement

The flow expressed in this statement can be thought of as

expression1
while ( expression2 ) {
      statement
      expression3
}

Any of the expressions can be missing. A missing expression2 is equivalent to

while ( 1 )

The second form of the for statement concerns associative arrays. A syntactical feature for these arrays (forms of which are available in the standard awk and gawk utilities) is available in spec as of release 4.01.05. The construction

for ( identifier in assoc-array ) statement

will run through each element of the associative array assoc_array assigning to identifier the string value of the index of each element. Note, though, the order in which the elements are assigned should be considered arbitrary.

For two-dimensional associative arrays, the construction

for ( identifier in assoc-array[expr] ) statement

will step through each element of assoc-array having expr has the first index.

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