FORT77(1P) POSIX Programmer's Manual FORT77(1P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAMEfort77 — FORTRAN compiler (FORTRAN)
SYNOPSISfort77 [−c] [−g] [−L directory]... [−O optlevel] [−o outfile] [−s]
The fort77 utility is the interface to the FORTRAN compilation system;
it shall accept the full FORTRAN-77 language defined by the
ANSI X3.9‐1978 standard. The system conceptually consists of a compiler
and link editor. The files referenced by operands are compiled and
linked to produce an executable file. It is unspecified whether the
linking occurs entirely within the operation of fort77; some implemen‐
tations may produce objects that are not fully resolved until the file
If the −c option is present, for all pathname operands of the form
file.f, the files:
shall be created or overwritten as the result of successful compila‐
tion. If the −c option is not specified, it is unspecified whether such
.o files are created or deleted for the file.f operands.
If there are no options that prevent link editing (such as −c) and all
operands compile and link without error, the resulting executable file
shall be written into the file named by the −o option (if present) or
to the file a.out. The executable file shall be created as specified
in the System Interfaces volume of POSIX.1‐2008, except that the file
permissions shall be set to: S_IRWXO | S_IRWXG | S_IRWXU
and that the bits specified by the umask of the process shall be
The fort77 utility shall conform to the Base Definitions volume of
POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines, except that:
* The −l library operands have the format of options, but their posi‐
tion within a list of operands affects the order in which libraries
* The order of specifying the multiple −L options is significant.
* Conforming applications shall specify each option separately; that
is, grouping option letters (for example, −cg) need not be recog‐
nized by all implementations.
The following options shall be supported:
−c Suppress the link-edit phase of the compilation, and do not
remove any object files that are produced.
−g Produce symbolic information in the object or executable
files; the nature of this information is unspecified, and may
be modified by implementation-defined interactions with other
−s Produce object or executable files, or both, from which sym‐
bolic and other information not required for proper execution
using the exec family of functions defined in the System
Interfaces volume of POSIX.1‐2008 has been removed
(stripped). If both −g and −s options are present, the
action taken is unspecified.
Use the pathname outfile, instead of the default a.out, for
the executable file produced. If the −o option is present
with −c, the result is unspecified.
Change the algorithm of searching for the libraries named in
−l operands to look in the directory named by the directory
pathname before looking in the usual places. Directories
named in −L options shall be searched in the specified order.
At least ten instances of this option shall be supported in a
single fort77 command invocation. If a directory specified by
a −L option contains a file named libf.a, the results are
Specify the level of code optimization. If the optlevel
option-argument is the digit '0', all special code optimiza‐
tions shall be disabled. If it is the digit '1', the nature
of the optimization is unspecified. If the −O option is omit‐
ted, the nature of the system's default optimization is
unspecified. It is unspecified whether code generated in the
presence of the −O 0 option is the same as that generated
when −O is omitted. Other optlevel values may be supported.
−w Suppress warnings.
Multiple instances of −L options can be specified.
An operand is either in the form of a pathname or the form −l library.
At least one operand of the pathname form shall be specified. The fol‐
lowing operands shall be supported:
file.f The pathname of a FORTRAN source file to be compiled and
optionally passed to the link editor. The filename operand
shall be of this form if the −c option is used.
file.a A library of object files typically produced by ar, and
passed directly to the link editor. Implementations may rec‐
ognize implementation-defined suffixes other than .a as
denoting object file libraries.
file.o An object file produced by fort77 −c and passed directly to
the link editor. Implementations may recognize implementa‐
tion-defined suffixes other than .o as denoting object files.
The processing of other files is implementation-defined.
(The letter ell.) Search the library named:
A library is searched when its name is encountered, so the
placement of a −l operand is significant. Several standard
libraries can be specified in this manner, as described in
the EXTENDED DESCRIPTION section. Implementations may recog‐
nize implementation-defined suffixes other than .a as denot‐
The input file shall be one of the following: a text file containing
FORTRAN source code; an object file in the format produced by fort77
−c; or a library of object files, in the format produced by archiving
zero or more object files, using ar. Implementations may supply addi‐
tional utilities that produce files in these formats. Additional input
files are implementation-defined.
A <tab> encountered within the first six characters on a line of source
code shall cause the compiler to interpret the following character as
if it were the seventh character on the line (that is, in column 7).
The following environment variables shall affect the execution of
LANG Provide a default value for the internationalization vari‐
ables that are unset or null. (See the Base Definitions vol‐
ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
ables for the precedence of internationalization variables
used to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of
all the other internationalization variables.
LC_CTYPE Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments and input
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard
NLSPATH Determine the location of message catalogs for the processing
TMPDIR Determine the pathname that should override the default
directory for temporary files, if any.
The standard error shall be used only for diagnostic messages. If more
than one file operand ending in .f (or possibly other unspecified suf‐
fixes) is given, for each such file:
may be written to allow identification of the diagnostic message with
the appropriate input file.
This utility may produce warning messages about certain conditions that
do not warrant returning an error (non-zero) exit value.
Object files, listing files, and executable files shall be produced in
The fort77 utility shall recognize the following −l operand for the
−l f This library contains all functions referenced in the
ANSI X3.9‐1978 standard. This operand shall not be required
to be present to cause a search of this library.
In the absence of options that inhibit invocation of the link editor,
such as −c, the fort77 utility shall cause the equivalent of a −l f op‐
erand to be passed to the link editor as the last −l operand, causing
it to be searched after all other object files and libraries are
It is unspecified whether the library libf.a exists as a regular file.
The implementation may accept as −l operands names of objects that do
not exist as regular files.
The FORTRAN compiler and link editor shall support the significance of
external symbols up to a length of at least 31 bytes; case folding is
permitted. The action taken upon encountering symbols exceeding the
implementation-defined maximum symbol length is unspecified.
The compiler and link editor shall support a minimum of 511 external
symbols per source or object file, and a minimum of 4095 external sym‐
bols total. A diagnostic message is written to standard output if the
implementation-defined limit is exceeded; other actions are unspeci‐
The following exit values shall be returned:
0 Successful compilation or link edit.
>0 An error occurred.
CONSEQUENCES OF ERRORS
When fort77 encounters a compilation error, it shall write a diagnostic
to standard error and continue to compile other source code operands.
It shall return a non-zero exit status, but it is implementation-
defined whether an object module is created. If the link edit is unsuc‐
cessful, a diagnostic message shall be written to standard error, and
fort77 shall exit with a non-zero status.
The following sections are informative.
The following usage example compiles xyz.f and creates the executable
fort77 −o foo xyz.f
The following example compiles xyz.f and creates the object file xyz.o:
fort77 −c xyz.f
The following example compiles xyz.f and creates the executable file
The following example compiles xyz.f, links it with b.o, and creates
the executable a.out:
fort77 xyz.f b.o
The name of this utility was chosen as fort77 to parallel the renaming
of the C compiler. The name f77 was not chosen to avoid problems with
historical implementations. The ANSI X3.9‐1978 standard was selected as
a normative reference because the ISO/IEC version of FORTRAN-77 has
been superseded by the ISO/IEC 1539:1991 standard.
The file inclusion and symbol definition #define mechanisms used by the
c99 utility were not included in this volume of POSIX.1‐2008—even
though they are commonly implemented—since there is no requirement that
the FORTRAN compiler use the C preprocessor.
The −onetrip option was not included in this volume of POSIX.1‐2008,
even though many historical compilers support it, because it is derived
from FORTRAN-66; it is an anachronism that should not be perpetuated.
Some implementations produce compilation listings. This aspect of FOR‐
TRAN has been left unspecified because there was controversy concerning
the various methods proposed for implementing it: a −V option over‐
lapped with historical vendor practice and a naming convention of cre‐
ating files with .l suffixes collided with historical lex file naming
There is no −I option in this version of this volume of POSIX.1‐2008 to
specify a directory for file inclusion. An INCLUDE directive has been a
part of the Fortran-90 discussions, but an interface supporting that
standard is not in the current scope.
It is noted that many FORTRAN compilers produce an object module even
when compilation errors occur; during a subsequent compilation, the
compiler may patch the object module rather than recompiling all the
code. Consequently, it is left to the implementor whether or not an
object file is created.
A reference to MIL-STD-1753 was removed from an early proposal in
response to a request from the POSIX FORTRAN-binding standard develop‐
ers. It was not the intention of the standard developers to require
certification of the FORTRAN compiler, and IEEE Std 1003.9‐1992 does
not specify the military standard or any special preprocessing require‐
ments. Furthermore, use of that document would have been inappropriate
for an international standard.
The specification of optimization has been subject to changes through
early proposals. At one time, −O and −N were Booleans: optimize and do
not optimize (with an unspecified default). Some historical practice
led this to be changed to:
−O 0 No optimization.
−O 1 Some level of optimization.
−O n Other, unspecified levels of optimization.
It is not always clear whether ``good code generation'' is the same
thing as optimization. Simple optimizations of local actions do not
usually affect the semantics of a program. The −O 0 option has been
included to accommodate the very particular nature of scientific calcu‐
lations in a highly optimized environment; compilers make errors. Some
degree of optimization is expected, even if it is not documented here,
and the ability to shut it off completely could be important when port‐
ing an application. An implementation may treat −O 0 as ``do less than
normal'' if it wishes, but this is only meaningful if any of the opera‐
tions it performs can affect the semantics of a program. It is highly
dependent on the implementation whether doing less than normal is logi‐
cal. It is not the intent of the −O 0 option to ask for inefficient
code generation, but rather to assure that any semantically visible
optimization is suppressed.
The specification of standard library access is consistent with the C
compiler specification. Implementations are not required to have
/usr/lib/libf.a, as many historical implementations do, but if not they
are required to recognize f as a token.
External symbol size limits are in normative text; conforming applica‐
tions need to know these limits. However, the minimum maximum symbol
length should be taken as a constraint on a conforming application, not
on an implementation, and consequently the action taken for a symbol
exceeding the limit is unspecified. The minimum size for the external
symbol table was added for similar reasons.
The CONSEQUENCES OF ERRORS section clearly specifies the behavior of
the compiler when compilation or link-edit errors occur. The behavior
of several historical implementations was examined, and the choice was
made to be silent on the status of the executable, or a.out, file in
the face of compiler or linker errors. If a linker writes the exe‐
cutable file, then links it on disk with lseek()s and write()s, the
partially linked executable file can be left on disk and its execute
bits turned off if the link edit fails. However, if the linker links
the image in memory before writing the file to disk, it need not touch
the executable file (if it already exists) because the link edit fails.
Since both approaches are historical practice, a conforming application
shall rely on the exit status of fort77, rather than on the existence
or mode of the executable file.
The −g and −s options are not specified as mutually-exclusive. Histori‐
cally, these two options have been mutually-exclusive, but because both
are so loosely specified, it seemed appropriate to leave their interac‐
The requirement that conforming applications specify compiler options
separately is to reserve the multi-character option name space for ven‐
dor-specific compiler options, which are known to exist in many histor‐
ical implementations. Implementations are not required to recognize,
for example, −gc as if it were −g −c; nor are they forbidden from doing
so. The SYNOPSIS shows all of the options separately to highlight this
requirement on applications.
Echoing filenames to standard error is considered a diagnostic message
because it would otherwise be difficult to associate an error message
with the erring file. They are described with ``may'' to allow imple‐
mentations to use other methods of identifying files and to parallel
the description in c99.
A compilation system based on the ISO/IEC 1539:1991 standard may be
considered for a future version; it may have a different utility name
ar, asa, c99, umask
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Section 12.2, Utility Syntax Guidelines
The System Interfaces volume of POSIX.1‐2008, exec
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
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