(gawk.info.gz) Command Line
(gawk.info.gz) Invoking Gawk
(gawk.info.gz) Other Arguments
11.2 Command-Line Options
Options begin with a dash and consist of a single character. GNU-style
long options consist of two dashes and a keyword. The keyword can be
abbreviated, as long as the abbreviation allows the option to be
uniquely identified. If the option takes an argument, then the keyword
is either immediately followed by an equals sign (`=') and the
argument's value, or the keyword and the argument's value are separated
by whitespace. If a particular option with a value is given more than
once, it is the last value that counts.
Each long option for `gawk' has a corresponding POSIX-style option.
The long and short options are interchangeable in all contexts. The
options and their meanings are as follows:
Sets the `FS' variable to FS ( Field Separators).
Indicates that the `awk' program is to be found in SOURCE-FILE
instead of in the first non-option argument.
Sets the variable VAR to the value VAL _before_ execution of the
program begins. Such variable values are available inside the
`BEGIN' rule ( Other Arguments).
The `-v' option can only set one variable, but it can be used more
than once, setting another variable each time, like this: `awk
-v foo=1 -v bar=2 ...'.
*Caution:* Using `-v' to set the values of the built-in variables
may lead to surprising results. `awk' will reset the values of
those variables as it needs to, possibly ignoring any predefined
value you may have given.
Sets various memory limits to the value N. The `f' flag sets the
maximum number of fields and the `r' flag sets the maximum record
size. These two flags and the `-m' option are from the Bell
Laboratories research version of Unix `awk'. They are provided
for compatibility but otherwise ignored by `gawk', since `gawk'
has no predefined limits. (The Bell Laboratories `awk' no longer
needs these options; it continues to accept them to avoid breaking
Following the POSIX standard, implementation-specific options are
supplied as arguments to the `-W' option. These options also have
corresponding GNU-style long options. Note that the long options
may be abbreviated, as long as the abbreviations remain unique.
The full list of `gawk'-specific options is provided next.
Signals the end of the command-line options. The following
arguments are not treated as options even if they begin with `-'.
This interpretation of `--' follows the POSIX argument parsing
This is useful if you have file names that start with `-', or in
shell scripts, if you have file names that will be specified by
the user that could start with `-'.
The previous list described options mandated by the POSIX standard,
as well as options available in the Bell Laboratories version of `awk'.
The following list describes `gawk'-specific options:
Enables some optimizations on the internal representation of the
program. At the moment this includes just simple constant
folding. The `gawk' maintainer hopes to add more optimizations
Specifies "compatibility mode", in which the GNU extensions to the
`awk' language are disabled, so that `gawk' behaves just like the
Bell Laboratories research version of Unix `awk'. `--traditional'
is the preferred form of this option. POSIX/GNU, which
summarizes the extensions. Also see Compatibility Mode.
Print the short version of the General Public License and then
Just like `--copyright'. This option may disappear in a future
version of `gawk'.
Prints a sorted list of global variables, their types, and final
values to FILE. If no FILE is provided, `gawk' prints this list
to the file named `awkvars.out' in the current directory.
Having a list of all global variables is a good way to look for
typographical errors in your programs. You would also use this
option if you have a large program with a lot of functions, and
you want to be sure that your functions don't inadvertently use
global variables that you meant to be local. (This is a
particularly easy mistake to make with simple variable names like
`i', `j', etc.)
`-W exec FILE'
Similar to `-f', reads `awk' program text from FILE. There are
two differences. The fist is that this option also terminates
option processing; anything else on the command line is passed on
directly to the `awk' program. The second is that command line
variable assignments of the form `VAR=VALUE' are disallowed.
This option is particularly necessary for World Wide Web CGI
applications that pass arguments through the URL; using this
option prevents a malicious (or other) user from passing in
options, assignments, or `awk' source code (via `--source') to the
CGI application. This option should be used with `#!' scripts
( Executable Scripts), like so:
#! /usr/local/bin/gawk --exec
AWK PROGRAM HERE ...
Analyzes the source program and generates a GNU `gettext' Portable
Object file on standard output for all string constants that have
been marked for translation. Internationalization, for
information about this option.
Prints a "usage" message summarizing the short and long style
options that `gawk' accepts and then exit.
Warns about constructs that are dubious or nonportable to other
`awk' implementations. Some warnings are issued when `gawk' first
reads your program. Others are issued at runtime, as your program
executes. With an optional argument of `fatal', lint warnings
become fatal errors. This may be drastic, but its use will
certainly encourage the development of cleaner `awk' programs.
With an optional argument of `invalid', only warnings about things
that are actually invalid are issued. (This is not fully
Some warnings are only printed once, even if the dubious
constructs they warn about occur multiple times in your `awk'
program. Thus, when eliminating problems pointed out by `--lint',
you should take care to search for all occurrences of each
inappropriate construct. As `awk' programs are usually short,
doing so is not burdensome.
Warns about constructs that are not available in the original
version of `awk' from Version 7 Unix ( V7/SVR3.1).
Enable automatic interpretation of octal and hexadecimal values in
input data ( Nondecimal Data).
*Caution:* This option can severely break old programs. Use with
Operates in strict POSIX mode. This disables all `gawk'
extensions (just like `--traditional') and adds the following
* `\x' escape sequences are not recognized ( Escape
* Newlines do not act as whitespace to separate fields when
`FS' is equal to a single space ( Fields).
* Newlines are not allowed after `?' or `:' ( Conditional
* The synonym `func' for the keyword `function' is not
recognized ( Definition Syntax).
* The `**' and `**=' operators cannot be used in place of `^'
and `^=' ( Arithmetic Ops, and also Assignment
* Specifying `-Ft' on the command-line does not set the value
of `FS' to be a single TAB character ( Field
* The locale's decimal point character is used for parsing input
data ( Locales).
* The `fflush' built-in function is not supported ( I/O
If you supply both `--traditional' and `--posix' on the command
line, `--posix' takes precedence. `gawk' also issues a warning if
both options are supplied.
Enable profiling of `awk' programs ( Profiling). By
default, profiles are created in a file named `awkprof.out'. The
optional FILE argument allows you to specify a different file name
for the profile file.
When run with `gawk', the profile is just a "pretty printed"
version of the program. When run with `pgawk', the profile
contains execution counts for each statement in the program in the
left margin, and function call counts for each function.
Allows interval expressions ( Regexp Operators) in regexps.
Because interval expressions were traditionally not available in
`awk', `gawk' does not provide them by default. This prevents old
`awk' programs from breaking.
`-W source PROGRAM-TEXT'
Allows you to mix source code in files with source code that you
enter on the command line. Program source code is taken from the
PROGRAM-TEXT. This is particularly useful when you have library
functions that you want to use from your command-line programs
( AWKPATH Variable).
This option forces the use of the locale's decimal point character
when parsing numeric input data ( Locales).
Prints version information for this particular copy of `gawk'.
This allows you to determine if your copy of `gawk' is up to date
with respect to whatever the Free Software Foundation is currently
distributing. It is also useful for bug reports ( Bugs).
As long as program text has been supplied, any other options are
flagged as invalid with a warning message but are otherwise ignored.
In compatibility mode, as a special case, if the value of FS supplied
to the `-F' option is `t', then `FS' is set to the TAB character
(`"\t"'). This is true only for `--traditional' and not for `--posix'
( Field Separators).
The `-f' option may be used more than once on the command line. If
it is, `awk' reads its program source from all of the named files, as
if they had been concatenated together into one big file. This is
useful for creating libraries of `awk' functions. These functions can
be written once and then retrieved from a standard place, instead of
having to be included into each individual program. (As mentioned in
Definition Syntax, function names must be unique.)
Library functions can still be used, even if the program is entered
at the terminal, by specifying `-f /dev/tty'. After typing your
program, type `Ctrl-d' (the end-of-file character) to terminate it.
(You may also use `-f -' to read program source from the standard input
but then you will not be able to also use the standard input as a
source of data.)
Because it is clumsy using the standard `awk' mechanisms to mix
source file and command-line `awk' programs, `gawk' provides the
`--source' option. This does not require you to pre-empt the standard
input for your source code; it allows you to easily mix command-line
and library source code ( AWKPATH Variable).
If no `-f' or `--source' option is specified, then `gawk' uses the
first non-option command-line argument as the text of the program
If the environment variable `POSIXLY_CORRECT' exists, then `gawk'
behaves in strict POSIX mode, exactly as if you had supplied the
`--posix' command-line option. Many GNU programs look for this
environment variable to turn on strict POSIX mode. If `--lint' is
supplied on the command line and `gawk' turns on POSIX mode because of
`POSIXLY_CORRECT', then it issues a warning message indicating that
POSIX mode is in effect. You would typically set this variable in your
shell's startup file. For a Bourne-compatible shell (such as `bash'),
you would add these lines to the `.profile' file in your home directory:
For a `csh'-compatible shell,(1) you would add this line to the
`.login' file in your home directory:
setenv POSIXLY_CORRECT true
Having `POSIXLY_CORRECT' set is not recommended for daily use, but
it is good for testing the portability of your programs to other
---------- Footnotes ----------
(1) Not recommended.
(gawk.info.gz) Command Line
(gawk.info.gz) Invoking Gawk
(gawk.info.gz) Other Arguments
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