GNU Info
(gawk.info)Options
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:
`-F FS'
`--field-separator FS'
Sets the `FS' variable to FS (Note: Specifying How Fields Are
Separated.).
`-f SOURCE-FILE'
`--file SOURCE-FILE'
Indicates that the `awk' program is to be found in SOURCE-FILE
instead of in the first non-option argument.
`-v VAR=VAL'
`--assign VAR=VAL'
Sets the variable VAR to the value VAL _before_ execution of the
program begins. Such variable values are available inside the
`BEGIN' rule (Note: Other Command-Line 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.
`-mf N'
`-mr N'
Set 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
old programs.)
`-W GAWK-OPT'
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
conventions.
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:
`-W compat'
`-W traditional'
`--compat'
`--traditional'
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. Note: Extensions in `gawk'
Not in POSIX `awk', which summarizes the extensions.
Also see Note: Downward Compatibility and Debugging.
`-W copyright'
`--copyright'
Print the short version of the General Public License and then
exit.
`-W copyleft'
`--copyleft'
Just like `--copyright'. This option may disappear in a future
version of `gawk'.
`-W dump-variables[=FILE]'
`--dump-variables[=FILE]'
Print a sorted list of global variables, their types, and final
values to FILE. If no FILE is provided, `gawk' prints this list
to a file named `awkvars.out' in the current directory.
Having a list of all the 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', and so on.)
`-W gen-po'
`--gen-po'
Analyze the source program and generate a GNU `gettext' Portable
Object file on standard output for all string constants that have
been marked for translation. Note: Internationalization with
`gawk', for information about this option.
`-W help'
`-W usage'
`--help'
`--usage'
Print a "usage" message summarizing the short and long style
options that `gawk' accepts and then exit.
`-W lint[=fatal]'
`--lint[=fatal]'
Warn about constructs that are dubious or non-portable 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.
`-W lint-old'
`--lint-old'
Warn about constructs that are not available in the original
version of `awk' from Version 7 Unix (Note: Major Changes Between
V7 and SVR3.1.1.).
`-W non-decimal-data'
`--non-decimal-data'
Enable automatic interpretation of octal and hexadecimal values in
input data (Note: Allowing Non-Decimal Input Data.
).
*Caution:* This option can severely break old programs. Use with
care.
`-W posix'
`--posix'
Operate in strict POSIX mode. This disables all `gawk' extensions
(just like `--traditional') and adds the following additional
restrictions:
* `\x' escape sequences are not recognized (Note: Escape
Sequences).
* Newlines do not act as whitespace to separate fields when
`FS' is equal to a single space (*note Examining Fields:
Fields.).
* Newlines are not allowed after `?' or `:' (Note: Conditional
Expressions.).
* The synonym `func' for the keyword `function' is not
recognized (Note: Function Definition Syntax.
).
* The `**' and `**=' operators cannot be used in place of `^'
and `^=' (Note: Arithmetic Operators., and
also Note: Assignment Expressions.).
* Specifying `-Ft' on the command-line does not set the value
of `FS' to be a single tab character (Note: Specifying How
Fields Are Separated.).
* The `fflush' built-in function is not supported (Note:
Input/Output Functions.).
If you supply both `--traditional' and `--posix' on the
command-line, `--posix' takes precedence. `gawk' also issues a
warning if both options are supplied.
`-W profile[=FILE]'
`--profile[=FILE]'
Enable profiling of `awk' programs (Note: Profiling Your `awk'
Programs.). 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.
`-W re-interval'
`--re-interval'
Allow interval expressions (*note Regular Expression Operators:
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'
`--source PROGRAM-TEXT'
Program source code is taken from the PROGRAM-TEXT. This option
allows you to mix source code in files with source code that you
enter on the command-line. This is particularly useful when you
have library functions that you want to use from your command-line
programs (Note: The `AWKPATH' Environment Variable.
).
`-W version'
`--version'
Print 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 (Note: Reporting
Problems and 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 only true for `--traditional' and not for `--posix'
(Note: Specifying How Fields Are Separated.).
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
Note: Function 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 (*note The `AWKPATH' Environment Variable:
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
source code.
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:
POSIXLY_CORRECT=true
export POSIXLY_CORRECT
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
environments.
---------- Footnotes ----------
(1) Not recommended.
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