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 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. For brevity, the discussion below only refers to the traditional short options; however the long and short options are interchangeable in all contexts.

Each long option for gawk has a corresponding POSIX-style option. The options and their meanings are as follows:

-F fs

--field-separator fs

Sets the FS variable to fs (see section 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 (see section Other Command Line Arguments). The `-v' option can only set one variable, but you can use it more than once, setting another variable each time, like this: `awk -v foo=1 -v bar=2 ...'.

-mf NNN

-mr NNN

Set various memory limits to the value NNN. 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 Labs research version of Unix awk. They are provided for compatibility, but otherwise ignored by gawk, since gawk has no predefined limits.

-W gawk-opt

Following the POSIX standard, options that are implementation specific are supplied as arguments to the `-W' option. These options also have corresponding GNU style long options. See below.

--

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 which could start with `-'.

The following gawk-specific options are available:

-W traditional

-W compat

--traditional

--compat

Specifies compatibility mode, in which the GNU extensions to the awk language are disabled, so that gawk behaves just like the Bell Labs research version of Unix awk. `--traditional' is the preferred form of this option. See section Extensions in gawk Not in POSIX awk, which summarizes the extensions. Also see section Downward Compatibility and Debugging.

-W copyleft

-W copyright

--copyleft

--copyright

Print the short version of the General Public License, and then exit. This option may disappear in a future version of gawk.

-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

--lint

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 run-time, as your program executes.

-W lint-old

--lint-old

Warn about constructs that are not available in the original Version 7 Unix version of awk (see section Major Changes between V7 and SVR3.1).

-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 (see section Escape Sequences).
• Newlines do not act as whitespace to separate fields when FS is equal to a single space.
• The synonym func for the keyword function is not recognized (see section Function Definition Syntax).
• The operators `**' and `**=' cannot be used in place of `^' and `^=' (see section Arithmetic Operators, and also see section Assignment Expressions).
• Specifying `-Ft' on the command line does not set the value of FS to be a single tab character (see section Specifying How Fields are Separated).
• The fflush built-in function is not supported (see section Built-in Functions for Input/Output).

If you supply both `--traditional' and `--posix' on the command line, `--posix' will take precedence. gawk will also issue a warning if both options are supplied.

-W re-interval

--re-interval

Allow interval expressions (see section Regular Expression 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 wish to use from your command line programs (see section The AWKPATH Environment Variable).

-W version

--version

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 (see section Reporting Problems and Bugs).

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' (see section 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. Useful functions can be written once, and then retrieved from a standard place, instead of having to be included into each individual program.

You can type in a program at the terminal and still use library functions, by specifying `-f /dev/tty'. awk will read a file from the terminal to use as part of the awk program. After typing your program, type Control-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, and allows you to easily mix command line and library source code (see section The AWKPATH Environment Variable).

If no `-f' or `--source' option is specified, then gawk will use the first non-option command line argument as the text of the program source code.

If the environment variable POSIXLY_CORRECT exists, then gawk will behave 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 you supply `--lint' on the command line, and gawk turns on POSIX mode because of POSIXLY_CORRECT, then it will print 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,(17) you would add this line to the `.login' file in your home directory.

setenv POSIXLY_CORRECT true

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