Next: Other Arguments, Previous: Command Line, Up: Invoking Gawk [Contents][Index]
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, either the keyword is immediately followed by an equals sign (‘=’) and the argument’s value, or the keyword and the argument’s value are separated by whitespace (spaces or TABs). 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 short option.
The long and short options are
interchangeable in all contexts.
The following list describes options mandated by the POSIX standard:
-F fs
--field-separator fs
Set the FS
variable to fs
(see section Specifying How Fields Are Separated).
-f source-file
--file source-file
Read the awk
program source from source-file
instead of in the first nonoption argument.
This option may be given multiple times; the awk
program consists of the concatenation of the contents of
each specified source-file.
Files named with -f are treated as if they had ‘@namespace "awk"’ at their beginning. See section Changing The Namespace, for more information on this advanced feature.
-v var=val
--assign var=val
Set 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 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 initial value you may have given.
-W gawk-opt
Provide an implementation-specific option.
This is the POSIX convention for providing implementation-specific options.
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.
--
Signal 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 ‘-’.
It is also useful for passing options on to the awk
program; see Processing Command-Line Options.
The following list describes gawk
-specific options:
Cause gawk
to treat all input data as single-byte characters.
In addition, all output written with print
or printf
is treated as single-byte characters.
Normally, gawk
follows the POSIX standard and attempts to process
its input data according to the current locale (see section Where You Are Makes a Difference). This can often involve
converting multibyte characters into wide characters (internally), and
can lead to problems or confusion if the input data does not contain valid
multibyte characters. This option is an easy way to tell gawk
,
“Hands off my data!”
Specify compatibility mode, in which the GNU extensions to
the awk
language are disabled, so that gawk
behaves just
like BWK awk
.
See section Extensions in gawk
Not in POSIX awk
,
which summarizes the extensions.
Also see
Downward Compatibility and Debugging.
Print the short version of the General Public License and then exit.
=
file]Print a sorted list of global variables, their types, and final values to file. If no file is provided, print this list to a file named awkvars.out in the current directory. No space is allowed between the -d and file, if file is supplied.
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.)
=
file]Enable debugging of awk
programs
(see section Introduction to the gawk
Debugger).
By default, the debugger reads commands interactively from the keyboard
(standard input).
The optional file argument allows you to specify a file with a list
of commands for the debugger to execute noninteractively.
No space is allowed between the -D and file, if
file is supplied.
Provide program source code in 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 (see section The AWKPATH
Environment Variable).
Note that gawk
treats each string as if it ended with
a newline character (even if it doesn’t). This makes building
the total program easier.
CAUTION: Prior to version 5.0, there was no requirement that each program-text be a full syntactic unit. I.e., the following worked:
$ gawk -e 'BEGIN { a = 5 ;' -e 'print a }' -| 5However, this is no longer true. If you have any scripts that rely upon this feature, you should revise them.
This is because each program-text is treated as if it had ‘@namespace "awk"’ at its beginning. See section Changing The Namespace, for more information.
Similar to -f, read awk
program text from file.
There are two differences from -f:
awk
program.
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 -e) to the CGI application.11
This option should be used
with ‘#!’ scripts (see section Executable awk
Programs), like so:
#! /usr/local/bin/gawk -E awk program here …
Analyze the source program and
generate a GNU gettext
portable object template file on standard
output for all string constants that have been marked for translation.
See section Internationalization with gawk
,
for information about this option.
Print a “usage” message summarizing the short- and long-style options
that gawk
accepts and then exit.
Read an awk
source library from source-file. This option
is completely equivalent to using the @include
directive inside
your program. It is very similar to the -f option,
but there are two important differences. First, when -i is
used, the program source is not loaded if it has been previously
loaded, whereas with -f, gawk
always loads the file.
Second, because this option is intended to be used with code libraries,
gawk
does not recognize such files as constituting main program
input. Thus, after processing an -i argument, gawk
still expects to find the main source code via the -f option
or on the command line.
Files named with -i are treated as if they had ‘@namespace "awk"’ at their beginning. See section Changing The Namespace, for more information.
Load a dynamic extension named ext. Extensions
are stored as system shared libraries.
This option searches for the library using the AWKLIBPATH
environment variable. The correct library suffix for your platform will be
supplied by default, so it need not be specified in the extension name.
The extension initialization routine should be named dl_load()
.
An alternative is to use the @load
keyword inside the program to load
a shared library. This advanced feature is described in detail in Writing Extensions for gawk
.
=
value]Warn about constructs that are dubious or nonportable to
other awk
implementations.
No space is allowed between the -L and value, if
value is supplied.
Some warnings are issued when gawk
first reads your program. Others
are issued at runtime, as your program executes. The optional
argument may be one of the following:
fatal
Cause lint warnings become fatal errors.
This may be drastic, but its use will certainly encourage the
development of cleaner awk
programs.
invalid
Only issue warnings about things that are actually invalid are issued. (This is not fully implemented yet.)
no-ext
Disable warnings about gawk
extensions.
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.
Select arbitrary-precision arithmetic on numbers. This option has no effect
if gawk
is not compiled to use the GNU MPFR and MP libraries
(see section Arithmetic and Arbitrary-Precision Arithmetic with gawk
).
Enable automatic interpretation of octal and hexadecimal values in input data (see section Allowing Nondecimal Input Data).
CAUTION: This option can severely break old programs. Use with care. Also note that this option may disappear in a future version of
gawk
.
Force the use of the locale’s decimal point character when parsing numeric input data (see section Where You Are Makes a Difference).
=
file]Enable pretty-printing of awk
programs.
Implies --no-optimize.
By default, the output program is created in a file named awkprof.out
(see section Profiling Your awk
Programs).
The optional file argument allows you to specify a different
file name for the output.
No space is allowed between the -o and file, if
file is supplied.
NOTE: In the past, this option would also execute your program. This is no longer the case.
Enable gawk
’s default optimizations on the internal
representation of the program. At the moment, this includes just simple
constant folding.
Optimization is enabled by default. This option remains primarily for backwards compatibility. However, it may be used to cancel the effect of an earlier -s option (see later in this list).
=
file]Enable profiling of awk
programs
(see section Profiling Your awk
Programs).
Implies --no-optimize.
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.
No space is allowed between the -p and file, if
file is supplied.
The profile contains execution counts for each statement in the program in the left margin, and function call counts for each function.
Operate in strict POSIX mode. This disables all gawk
extensions (just like --traditional) and
disables all extensions not allowed by POSIX.
See section Common Extensions Summary for a summary of the extensions
in gawk
that are disabled by this option.
Also,
the following additional
restrictions apply:
FS
to be a single TAB character
(see section Specifying How Fields Are Separated).
If you supply both --traditional and --posix on the
command line, --posix takes precedence. gawk
issues a warning if both options are supplied.
Allow interval expressions
(see section Regular Expression Operators)
in regexps.
This is now gawk
’s default behavior.
Nevertheless, this option remains (both for backward compatibility
and for use in combination with --traditional).
Disable gawk
’s default optimizations on the internal
representation of the program.
Disable the system()
function,
input redirections with getline
,
output redirections with print
and printf
,
and dynamic extensions.
Also, disallow adding filenames to ARGV
that were
not there when gawk
started running.
This is particularly useful when you want to run awk
scripts
from questionable sources and need to make sure the scripts
can’t access your system (other than the specified input data files).
Warn about constructs that are not available in the original version of
awk
from Version 7 Unix
(see section Major Changes Between V7 and SVR3.1).
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
(see section Reporting Problems and Bugs).
--
Mark the end of all options.
Any command-line arguments following --
are placed in ARGV
,
even if they start with a minus sign.
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
(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. These functions
can be written once and then retrieved from a standard place, instead
of having to be included in each individual program.
The -i option is similar in this regard.
(As mentioned in
Function Definition Syntax,
function names must be unique.)
With standard awk
, library functions can still be used, even
if the program is entered at the keyboard,
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 -e option. This does not require you to
preempt the standard input for your source code, and it allows you to easily
mix command-line and library source code (see section The AWKPATH
Environment Variable).
As with -f, the -e and -i
options may also be used multiple times on the command line.
If no -f option (or -e option for gawk
)
is specified, then awk
uses the first nonoption command-line
argument as the text of the program source code. Arguments on
the command line that follow the program text are entered into the
ARGV
array; awk
does not continue to parse the
command line looking for options.
If the environment variable POSIXLY_CORRECT
exists,
then gawk
behaves in strict POSIX mode, exactly as if
you had supplied --posix.
Many GNU programs look for this environment variable to suppress
extensions that conflict with POSIX, but gawk
behaves
differently: it suppresses all extensions, even those that do not
conflict with POSIX, and behaves in
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 C shell-compatible shell,12 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.
For more detail,
please see Section 4.4 of RFC 3875. Also see the
explanatory note sent to the gawk
bug
mailing list.
Not recommended.
Next: Other Arguments, Previous: Command Line, Up: Invoking Gawk [Contents][Index]