File: gawk.info,  Node: User-modified,  Next: Auto-set,  Up: Built-in Variables

7.5.1 Built-in Variables That Control 'awk'
-------------------------------------------

The following is an alphabetical list of variables that you can change
to control how 'awk' does certain things.

   The variables that are specific to 'gawk' are marked with a pound
sign ('#').  These variables are 'gawk' extensions.  In other 'awk'
implementations or if 'gawk' is in compatibility mode (*note Options::),
they are not special.  (Any exceptions are noted in the description of
each variable.)

'BINMODE #'
     On non-POSIX systems, this variable specifies use of binary mode
     for all I/O. Numeric values of one, two, or three specify that
     input files, output files, or all files, respectively, should use
     binary I/O. A numeric value less than zero is treated as zero, and
     a numeric value greater than three is treated as three.
     Alternatively, string values of '"r"' or '"w"' specify that input
     files and output files, respectively, should use binary I/O. A
     string value of '"rw"' or '"wr"' indicates that all files should
     use binary I/O. Any other string value is treated the same as
     '"rw"', but causes 'gawk' to generate a warning message.  'BINMODE'
     is described in more detail in *note PC Using::.  'mawk' (*note
     Other Versions::) also supports this variable, but only using
     numeric values.

'CONVFMT'
     A string that controls the conversion of numbers to strings (*note
     Conversion::).  It works by being passed, in effect, as the first
     argument to the 'sprintf()' function (*note String Functions::).
     Its default value is '"%.6g"'.  'CONVFMT' was introduced by the
     POSIX standard.

'FIELDWIDTHS #'
     A space-separated list of columns that tells 'gawk' how to split
     input with fixed columnar boundaries.  Starting in version 4.2,
     each field width may optionally be preceded by a colon-separated
     value specifying the number of characters to skip before the field
     starts.  Assigning a value to 'FIELDWIDTHS' overrides the use of
     'FS' and 'FPAT' for field splitting.  *Note Constant Size:: for
     more information.

'FPAT #'
     A regular expression (as a string) that tells 'gawk' to create the
     fields based on text that matches the regular expression.
     Assigning a value to 'FPAT' overrides the use of 'FS' and
     'FIELDWIDTHS' for field splitting.  *Note Splitting By Content::
     for more information.

'FS'
     The input field separator (*note Field Separators::).  The value is
     a single-character string or a multicharacter regular expression
     that matches the separations between fields in an input record.  If
     the value is the null string ('""'), then each character in the
     record becomes a separate field.  (This behavior is a 'gawk'
     extension.  POSIX 'awk' does not specify the behavior when 'FS' is
     the null string.  Nonetheless, some other versions of 'awk' also
     treat '""' specially.)

     The default value is '" "', a string consisting of a single space.
     As a special exception, this value means that any sequence of
     spaces, TABs, and/or newlines is a single separator.  It also
     causes spaces, TABs, and newlines at the beginning and end of a
     record to be ignored.

     You can set the value of 'FS' on the command line using the '-F'
     option:

          awk -F, 'PROGRAM' INPUT-FILES

     If 'gawk' is using 'FIELDWIDTHS' or 'FPAT' for field splitting,
     assigning a value to 'FS' causes 'gawk' to return to the normal,
     'FS'-based field splitting.  An easy way to do this is to simply
     say 'FS = FS', perhaps with an explanatory comment.

'IGNORECASE #'
     If 'IGNORECASE' is nonzero or non-null, then all string comparisons
     and all regular expression matching are case-independent.  This
     applies to regexp matching with '~' and '!~', the 'gensub()',
     'gsub()', 'index()', 'match()', 'patsplit()', 'split()', and
     'sub()' functions, record termination with 'RS', and field
     splitting with 'FS' and 'FPAT'.  However, the value of 'IGNORECASE'
     does _not_ affect array subscripting and it does not affect field
     splitting when using a single-character field separator.  *Note
     Case-sensitivity::.

'LINT #'
     When this variable is true (nonzero or non-null), 'gawk' behaves as
     if the '--lint' command-line option is in effect (*note Options::).
     With a value of '"fatal"', lint warnings become fatal errors.  With
     a value of '"invalid"', only warnings about things that are
     actually invalid are issued.  (This is not fully implemented yet.)
     Any other true value prints nonfatal warnings.  Assigning a false
     value to 'LINT' turns off the lint warnings.

     This variable is a 'gawk' extension.  It is not special in other
     'awk' implementations.  Unlike with the other special variables,
     changing 'LINT' does affect the production of lint warnings, even
     if 'gawk' is in compatibility mode.  Much as the '--lint' and
     '--traditional' options independently control different aspects of
     'gawk''s behavior, the control of lint warnings during program
     execution is independent of the flavor of 'awk' being executed.

'OFMT'
     A string that controls conversion of numbers to strings (*note
     Conversion::) for printing with the 'print' statement.  It works by
     being passed as the first argument to the 'sprintf()' function
     (*note String Functions::).  Its default value is '"%.6g"'.
     Earlier versions of 'awk' used 'OFMT' to specify the format for
     converting numbers to strings in general expressions; this is now
     done by 'CONVFMT'.

'OFS'
     The output field separator (*note Output Separators::).  It is
     output between the fields printed by a 'print' statement.  Its
     default value is '" "', a string consisting of a single space.

'ORS'
     The output record separator.  It is output at the end of every
     'print' statement.  Its default value is '"\n"', the newline
     character.  (*Note Output Separators::.)

'PREC #'
     The working precision of arbitrary-precision floating-point
     numbers, 53 bits by default (*note Setting precision::).

'ROUNDMODE #'
     The rounding mode to use for arbitrary-precision arithmetic on
     numbers, by default '"N"' ('roundTiesToEven' in the IEEE 754
     standard; *note Setting the rounding mode::).

'RS'
     The input record separator.  Its default value is a string
     containing a single newline character, which means that an input
     record consists of a single line of text.  It can also be the null
     string, in which case records are separated by runs of blank lines.
     If it is a regexp, records are separated by matches of the regexp
     in the input text.  (*Note Records::.)

     The ability for 'RS' to be a regular expression is a 'gawk'
     extension.  In most other 'awk' implementations, or if 'gawk' is in
     compatibility mode (*note Options::), just the first character of
     'RS''s value is used.

'SUBSEP'
     The subscript separator.  It has the default value of '"\034"' and
     is used to separate the parts of the indices of a multidimensional
     array.  Thus, the expression 'foo["A", "B"]' really accesses
     'foo["A\034B"]' (*note Multidimensional::).

'TEXTDOMAIN #'
     Used for internationalization of programs at the 'awk' level.  It
     sets the default text domain for specially marked string constants
     in the source text, as well as for the 'dcgettext()',
     'dcngettext()', and 'bindtextdomain()' functions (*note
     Internationalization::).  The default value of 'TEXTDOMAIN' is
     '"messages"'.