man gfortran Command

Man page for apt-get gfortran Command

Man Page for gfortran in Linux

Ubuntu Man Command : man gfortran

Man Gfortran  Command

This tutorial shows the man page for man gfortran in linux.

Open terminal with 'su' access and type the command as shown below:
man gfortran

Result of the Command Execution shown below:

GFORTRAN(1)                                                                      GNU                                                                     GFORTRAN(1)



NAME
gfortran GNU Fortran compiler

SYNOPSIS
gfortran [ c| S| E]
[ g] [ pg] [ Olevel]
[ Wwarn...] [ pedantic]
[ Idir...] [ Ldir...]
[ Dmacro[=defn]...] [ Umacro]
[ foption...]
[ mmachine option...]
[ o outfile] infile...

Only the most useful options are listed here; see below for the remainder.

DESCRIPTION
The gfortran command supports all the options supported by the gcc command. Only options specific to GNU Fortran are documented here.

All GCC and GNU Fortran options are accepted both by gfortran and by gcc (as well as any other drivers built at the same time, such as g++), since adding GNU
Fortran to the GCC distribution enables acceptance of GNU Fortran options by all of the relevant drivers.

In some cases, options have positive and negative forms; the negative form of ffoo would be fno foo. This manual documents only one of these two forms,
whichever one is not the default.

OPTIONS
Here is a summary of all the options specific to GNU Fortran, grouped by type. Explanations are in the following sections.

Fortran Language Options
fall intrinsics ffree form fno fixed form fdollar ok fimplicit none fmax identifier length std=std fd lines as code fd lines as comments
ffixed line length n ffixed line length none ffree line length n ffree line length none fdefault double 8 fdefault integer 8 fdefault real 8
fcray pointer fopenmp fno range check fbackslash fmodule private

Preprocessing Options
cpp dD dI dM dN dU fworking directory imultilib dir iprefix file isysroot dir iquote isystem dir nocpp nostdinc undef Aquestion=answer
A question[=answer] C CC Dmacro[=defn] Umacro H P

Error and Warning Options
fmax errors=n fsyntax only pedantic pedantic errors Wall Waliasing Wampersand Warray bounds Wcharacter truncation Wconversion
Wimplicit interface Wline truncation Wintrinsics std Wsurprising Wno tabs Wunderflow Wunused parameter Wintrinsics shadow Wno align commons

Debugging Options
fdump parse tree ffpe trap=list fdump core fbacktrace

Directory Options
Idir Jdir Mdir fintrinsic modules path dir

Link Options
static libgfortran

Runtime Options
fconvert=conversion fno range check frecord marker=length fmax subrecord length=length fsign zero

Code Generation Options
fno automatic ff2c fno underscoring fsecond underscore fbounds check fcheck array temporaries fmax array constructor =n fmax stack var size=n
fpack derived frepack arrays fshort enums fexternal blas fblas matmul limit=n frecursive finit local zero finit integer=n
finit real=<zero|inf| inf|nan> finit logical=<true|false> finit character=n fno align commons

Options controlling Fortran dialect
The following options control the details of the Fortran dialect accepted by the compiler:

ffree form
ffixed form
Specify the layout used by the source file. The free form layout was introduced in Fortran 90. Fixed form was traditionally used in older Fortran
programs. When neither option is specified, the source form is determined by the file extension.

fall intrinsics
This option causes all intrinsic procedures (including the GNU specific extensions) to be accepted. This can be useful with std=f95 to force standard
compliance but get access to the full range of intrinsics available with gfortran. As a consequence, Wintrinsics std will be ignored and no user
defined procedure with the same name as any intrinsic will be called except when it is explicitly declared "EXTERNAL".

fd lines as code
fd lines as comments
Enable special treatment for lines beginning with "d" or "D" in fixed form sources. If the fd lines as code option is given they are treated as if the
first column contained a blank. If the fd lines as comments option is given, they are treated as comment lines.

fdefault double 8
Set the "DOUBLE PRECISION" type to an 8 byte wide type. If fdefault real 8 is given, "DOUBLE PRECISION" would instead be promoted to 16 bytes if
possible, and fdefault double 8 can be used to prevent this. The kind of real constants like "1.d0" will not be changed by fdefault real 8 though, so
also fdefault double 8 does not affect it.

fdefault integer 8
Set the default integer and logical types to an 8 byte wide type. Do nothing if this is already the default. This option also affects the kind of
integer constants like 42.

fdefault real 8
Set the default real type to an 8 byte wide type. Do nothing if this is already the default. This option also affects the kind of non double real
constants like 1.0, and does promote the default width of "DOUBLE PRECISION" to 16 bytes if possible, unless " fdefault double 8" is given, too.

fdollar ok
Allow $ as a valid character in a symbol name.

fbackslash
Change the interpretation of backslashes in string literals from a single backslash character to "C style" escape characters. The following combinations
are expanded "", "", "", "
", "
", "", "", "\", and "" to the ASCII characters alert, backspace, form feed, newline, carriage return,
horizontal tab, vertical tab, backslash, and NUL, respectively. Additionally, "\x"nn, "\u"nnnn and "\U"nnnnnnnn (where each n is a hexadecimal digit)
are translated into the Unicode characters corresponding to the specified code points. All other combinations of a character preceded by \ are
unexpanded.

fmodule private
Set the default accessibility of module entities to "PRIVATE". Use associated entities will not be accessible unless they are explicitly declared as
"PUBLIC".

ffixed line length n
Set column after which characters are ignored in typical fixed form lines in the source file, and through which spaces are assumed (as if padded to that
length) after the ends of short fixed form lines.

Popular values for n include 72 (the standard and the default), 80 (card image), and 132 (corresponding to "extended source" options in some popular
compilers). n may also be none, meaning that the entire line is meaningful and that continued character constants never have implicit spaces appended to
them to fill out the line. ffixed line length 0 means the same thing as ffixed line length none.

ffree line length n
Set column after which characters are ignored in typical free form lines in the source file. The default value is 132. n may be none, meaning that the
entire line is meaningful. ffree line length 0 means the same thing as ffree line length none.

fmax identifier length=n
Specify the maximum allowed identifier length. Typical values are 31 (Fortran 95) and 63 (Fortran 2003 and Fortran 2008).

fimplicit none
Specify that no implicit typing is allowed, unless overridden by explicit "IMPLICIT" statements. This is the equivalent of adding "implicit none" to the
start of every procedure.

fcray pointer
Enable the Cray pointer extension, which provides C like pointer functionality.

fopenmp
Enable the OpenMP extensions. This includes OpenMP "!$omp" directives in free form and "c$omp", *$omp and "!$omp" directives in fixed form, "!$"
conditional compilation sentinels in free form and "c$", "*$" and "!$" sentinels in fixed form, and when linking arranges for the OpenMP runtime library
to be linked in. The option fopenmp implies frecursive.

fno range check
Disable range checking on results of simplification of constant expressions during compilation. For example, GNU Fortran will give an error at compile
time when simplifying "a = 1. / 0". With this option, no error will be given and "a" will be assigned the value "+Infinity". If an expression evaluates
to a value outside of the relevant range of [" HUGE()":"HUGE()"], then the expression will be replaced by " Inf" or "+Inf" as appropriate. Similarly,
"DATA i/Z'FFFFFFFF'/" will result in an integer overflow on most systems, but with fno range check the value will "wrap around" and "i" will be
initialized to 1 instead.

std=std
Specify the standard to which the program is expected to conform, which may be one of f95, f2003, f2008, gnu, or legacy. The default value for std is
gnu, which specifies a superset of the Fortran 95 standard that includes all of the extensions supported by GNU Fortran, although warnings will be given
for obsolete extensions not recommended for use in new code. The legacy value is equivalent but without the warnings for obsolete extensions, and may be
useful for old non standard programs. The f95, f2003 and f2008 values specify strict conformance to the Fortran 95, Fortran 2003 and Fortran 2008
standards, respectively; errors are given for all extensions beyond the relevant language standard, and warnings are given for the Fortran 77 features
that are permitted but obsolescent in later standards.

Enable and customize preprocessing
Preprocessor related options. See section Preprocessing and conditional compilation for more detailed information on preprocessing in gfortran.

cpp
nocpp
Enable preprocessing. The preprocessor is automatically invoked if the file extension is .fpp, .FPP, .F, .FOR, .FTN, .F90, .F95, .F03 or .F08. Use this
option to manually enable preprocessing of any kind of Fortran file.

To disable preprocessing of files with any of the above listed extensions, use the negative form: nocpp.

The preprocessor is run in traditional mode, be aware that any restrictions of the file format, e.g. fixed form line width, apply for preprocessed output
as well.

dM Instead of the normal output, generate a list of '


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