The GNU Fortran Compiler

Table of Contents

• Introduction
• 1 Introduction
  • 1.1 About GNU Fortran
  • 1.2 GNU Fortran and GCC
  • 1.3 Preprocessing and conditional compilation
  • 1.4 GNU Fortran and G77
  • 1.5 Project Status
  • 1.6 Standards
    • 1.6.1 Varying Length Character Strings
• 2 GNU Fortran Command Options
  • 2.1 Option summary
  • 2.2 Options controlling Fortran dialect
  • 2.3 Enable and customize preprocessing
  • 2.4 Options to request or suppress errors and warnings
  • 2.5 Options for debugging your program or GNU Fortran
  • 2.6 Options for directory search
  • 2.7 Influencing the linking step
  • 2.8 Influencing runtime behavior
  • 2.9 Options for code generation conventions
  • 2.10 Environment variables affecting gfortran
• 3 Runtime: Influencing runtime behavior with environment variables
  • 3.1 TMPDIR—Directory for scratch files
  • 3.2 GFORTRAN_STDIN_UNIT—Unit number for standard input
  • 3.3 GFORTRAN_STDOUT_UNIT—Unit number for standard output
  • 3.4 GFORTRAN_STDERR_UNIT—Unit number for standard error
  • 3.5 GFORTRAN_UNBUFFERED_ALL—Do not buffer I/O on all units
  • 3.6 GFORTRAN_UNBUFFERED_PRECONNECTED—Do not buffer I/O on preconnected units
  • 3.7 GFORTRAN_SHOW_LOCUS—Show location for runtime errors
  • 3.8 GFORTRAN_OPTIONAL_PLUS—Print leading + where permitted
  • 3.9 GFORTRAN_DEFAULT_RECL—Default record length for new files
  • 3.10 GFORTRAN_LIST_SEPARATOR—Separator for list output
  • 3.11 GFORTRAN_CONVERT_UNIT—Set endianness for unformatted I/O
  • 3.12 GFORTRAN_ERROR_BACKTRACE—Show backtrace on run-time errors
• 4 Fortran 2003 and 2008 Status
  • 4.1 Fortran 2003 status
  • 4.2 Fortran 2008 status
  • 4.3 Technical Specification 29113 Status
• 5 Compiler Characteristics
  • 5.1 KIND Type Parameters
  • 5.2 Internal representation of LOGICAL variables
  • 5.3 Thread-safety of the runtime library
  • 5.4 Data consistency and durability
• 6 Extensions
  • 6.1 Extensions implemented in GNU Fortran
    • 6.1.1 Old-style kind specifications
    • 6.1.2 Old-style variable initialization
    • 6.1.3 Extensions to namelist
    • 6.1.4 X format descriptor without count field
    • 6.1.5 Commas in FORMAT specifications
    • 6.1.6 Missing period in FORMAT specifications
    • 6.1.7 I/O item lists
    • 6.1.8 Q exponent-letter
    • 6.1.9 BOZ literal constants
    • 6.1.10 Real array indices
    • 6.1.11 Unary operators
    • 6.1.12 Implicitly convert LOGICAL and INTEGER values
    • 6.1.13 Hollerith constants support
    • 6.1.14 Cray pointers
    • 6.1.15 CONVERT specifier
    • 6.1.16 OpenMP
    • 6.1.17 Argument list functions %VAL, %REF and %LOC
  • 6.2 Extensions not implemented in GNU Fortran
    • 6.2.1 STRUCTURE and RECORD
    • 6.2.2 ENCODE and DECODE statements
    • 6.2.3 Variable FORMAT expressions
    • 6.2.4 Alternate complex function syntax
    • 6.2.5 Volatile COMMON blocks
• 7 Mixed-Language Programming
  • 7.1 Interoperability with C
    • 7.1.1 Intrinsic Types
    • 7.1.2 Derived Types and struct
    • 7.1.3 Interoperable Global Variables
    • 7.1.4 Interoperable Subroutines and Functions
    • 7.1.5 Working with Pointers
    • 7.1.6 Further Interoperability of Fortran with C
  • 7.2 GNU Fortran Compiler Directives
  • 7.3 Non-Fortran Main Program
    • 7.3.1 _gfortran_set_args — Save command-line arguments
    • 7.3.2 _gfortran_set_options — Set library option flags
    • 7.3.3 _gfortran_set_convert — Set endian conversion
    • 7.3.4 _gfortran_set_record_marker — Set length of record markers
    • 7.3.5 _gfortran_set_fpe — Enable floating point exception traps
    • 7.3.6 _gfortran_set_max_subrecord_length — Set subrecord length
  • 7.4 Naming and argument-passing conventions
    • 7.4.1 Naming conventions
    • 7.4.2 Argument passing conventions
• 8 Intrinsic Procedures
  • 8.1 Introduction to intrinsic procedures
  • 8.2 ABORT — Abort the program
  • 8.3 ABS — Absolute value
  • 8.4 ACCESS — Checks file access modes
  • 8.5 ACHAR — Character in ASCII collating sequence
  • 8.6 ACOS — Arccosine function
  • 8.7 ACOSH — Inverse hyperbolic cosine function
  • 8.8 ADJUSTL — Left adjust a string
  • 8.9 ADJUSTR — Right adjust a string
  • 8.10 AIMAG — Imaginary part of complex number
  • 8.11 AINT — Truncate to a whole number
  • 8.12 ALARM — Execute a routine after a given delay
  • 8.13 ALL — All values in MASK along DIM are true
  • 8.14 ALLOCATED — Status of an allocatable entity
  • 8.15 AND — Bitwise logical AND
  • 8.16 ANINT — Nearest whole number
  • 8.17 ANY — Any value in MASK along DIM is true
  • 8.18 ASIN — Arcsine function
  • 8.19 ASINH — Inverse hyperbolic sine function
  • 8.20 ASSOCIATED — Status of a pointer or pointer/target pair
  • 8.21 ATAN — Arctangent function
  • 8.22 ATAN2 — Arctangent function
  • 8.23 ATANH — Inverse hyperbolic tangent function
  • 8.24 ATOMIC_DEFINE — Setting a variable atomically
  • 8.25 ATOMIC_REF — Obtaining the value of a variable atomically
  • 8.26 BACKTRACE — Show a backtrace
  • 8.27 BESSEL_J0 — Bessel function of the first kind of order 0
  • 8.28 BESSEL_J1 — Bessel function of the first kind of order 1
  • 8.29 BESSEL_JN — Bessel function of the first kind
  • 8.30 BESSEL_Y0 — Bessel function of the second kind of order 0
  • 8.31 BESSEL_Y1 — Bessel function of the second kind of order 1
  • 8.32 BESSEL_YN — Bessel function of the second kind
  • 8.33 BGE — Bitwise greater than or equal to
  • 8.34 BGT — Bitwise greater than
  • 8.35 BIT_SIZE — Bit size inquiry function
  • 8.36 BLE — Bitwise less than or equal to
  • 8.37 BLT — Bitwise less than
  • 8.38 BTEST — Bit test function
  • 8.39 C_ASSOCIATED — Status of a C pointer
  • 8.40 C_F_POINTER — Convert C into Fortran pointer
  • 8.41 C_F_PROCPOINTER — Convert C into Fortran procedure pointer
  • 8.42 C_FUNLOC — Obtain the C address of a procedure
  • 8.43 C_LOC — Obtain the C address of an object
  • 8.44 C_SIZEOF — Size in bytes of an expression
  • 8.45 CEILING — Integer ceiling function
  • 8.46 CHAR — Character conversion function
  • 8.47 CHDIR — Change working directory
  • 8.48 CHMOD — Change access permissions of files
  • 8.49 CMPLX — Complex conversion function
  • 8.50 COMMAND_ARGUMENT_COUNT — Get number of command line arguments
  • 8.51 COMPILER_OPTIONS — Options passed to the compiler
  • 8.52 COMPILER_VERSION — Compiler version string
  • 8.53 COMPLEX — Complex conversion function
  • 8.54 CONJG — Complex conjugate function
  • 8.55 COS — Cosine function
  • 8.56 COSH — Hyperbolic cosine function
  • 8.57 COUNT — Count function
  • 8.58 CPU_TIME — CPU elapsed time in seconds
  • 8.59 CSHIFT — Circular shift elements of an array
  • 8.60 CTIME — Convert a time into a string
  • 8.61 DATE_AND_TIME — Date and time subroutine
  • 8.62 DBLE — Double conversion function
  • 8.63 DCMPLX — Double complex conversion function
  • 8.64 DIGITS — Significant binary digits function
  • 8.65 DIM — Positive difference
  • 8.66 DOT_PRODUCT — Dot product function
  • 8.67 DPROD — Double product function
  • 8.68 DREAL — Double real part function
  • 8.69 DSHIFTL — Combined left shift
  • 8.70 DSHIFTR — Combined right shift
  • 8.71 DTIME — Execution time subroutine (or function)
  • 8.72 EOSHIFT — End-off shift elements of an array
  • 8.73 EPSILON — Epsilon function
  • 8.74 ERF — Error function
  • 8.75 ERFC — Error function
  • 8.76 ERFC_SCALED — Error function
  • 8.77 ETIME — Execution time subroutine (or function)
  • 8.78 EXECUTE_COMMAND_LINE — Execute a shell command
  • 8.79 EXIT — Exit the program with status.
  • 8.80 EXP — Exponential function
  • 8.81 EXPONENT — Exponent function
  • 8.82 EXTENDS_TYPE_OF — Query dynamic type for extension
  • 8.83 FDATE — Get the current time as a string
  • 8.84 FGET — Read a single character in stream mode from stdin
  • 8.85 FGETC — Read a single character in stream mode
  • 8.86 FLOOR — Integer floor function
  • 8.87 FLUSH — Flush I/O unit(s)
  • 8.88 FNUM — File number function
  • 8.89 FPUT — Write a single character in stream mode to stdout
  • 8.90 FPUTC — Write a single character in stream mode
  • 8.91 FRACTION — Fractional part of the model representation
  • 8.92 FREE — Frees memory
  • 8.93 FSEEK — Low level file positioning subroutine
  • 8.94 FSTAT — Get file status
  • 8.95 FTELL — Current stream position
  • 8.96 GAMMA — Gamma function
  • 8.97 GERROR — Get last system error message
  • 8.98 GETARG — Get command line arguments
  • 8.99 GET_COMMAND — Get the entire command line
  • 8.100 GET_COMMAND_ARGUMENT — Get command line arguments
  • 8.101 GETCWD — Get current working directory
  • 8.102 GETENV — Get an environmental variable
  • 8.103 GET_ENVIRONMENT_VARIABLE — Get an environmental variable
  • 8.104 GETGID — Group ID function
  • 8.105 GETLOG — Get login name
  • 8.106 GETPID — Process ID function
  • 8.107 GETUID — User ID function
  • 8.108 GMTIME — Convert time to GMT info
  • 8.109 HOSTNM — Get system host name
  • 8.110 HUGE — Largest number of a kind
  • 8.111 HYPOT — Euclidean distance function
  • 8.112 IACHAR — Code in ASCII collating sequence
  • 8.113 IALL — Bitwise AND of array elements
  • 8.114 IAND — Bitwise logical and
  • 8.115 IANY — Bitwise OR of array elements
  • 8.116 IARGC — Get the number of command line arguments
  • 8.117 IBCLR — Clear bit
  • 8.118 IBITS — Bit extraction
  • 8.119 IBSET — Set bit
  • 8.120 ICHAR — Character-to-integer conversion function
  • 8.121 IDATE — Get current local time subroutine (day/month/year)
  • 8.122 IEOR — Bitwise logical exclusive or
  • 8.123 IERRNO — Get the last system error number
  • 8.124 IMAGE_INDEX — Function that converts a cosubscript to an image index
  • 8.125 INDEX — Position of a substring within a string
  • 8.126 INT — Convert to integer type
  • 8.127 INT2 — Convert to 16-bit integer type
  • 8.128 INT8 — Convert to 64-bit integer type
  • 8.129 IOR — Bitwise logical or
  • 8.130 IPARITY — Bitwise XOR of array elements
  • 8.131 IRAND — Integer pseudo-random number
  • 8.132 IS_IOSTAT_END — Test for end-of-file value
  • 8.133 IS_IOSTAT_EOR — Test for end-of-record value
  • 8.134 ISATTY — Whether a unit is a terminal device.
  • 8.135 ISHFT — Shift bits
  • 8.136 ISHFTC — Shift bits circularly
  • 8.137 ISNAN — Test for a NaN
  • 8.138 ITIME — Get current local time subroutine (hour/minutes/seconds)
  • 8.139 KILL — Send a signal to a process
  • 8.140 KIND — Kind of an entity
  • 8.141 LBOUND — Lower dimension bounds of an array
  • 8.142 LCOBOUND — Lower codimension bounds of an array
  • 8.143 LEADZ — Number of leading zero bits of an integer
  • 8.144 LEN — Length of a character entity
  • 8.145 LEN_TRIM — Length of a character entity without trailing blank characters
  • 8.146 LGE — Lexical greater than or equal
  • 8.147 LGT — Lexical greater than
  • 8.148 LINK — Create a hard link
  • 8.149 LLE — Lexical less than or equal
  • 8.150 LLT — Lexical less than
  • 8.151 LNBLNK — Index of the last non-blank character in a string
  • 8.152 LOC — Returns the address of a variable
  • 8.153 LOG — Natural logarithm function
  • 8.154 LOG10 — Base 10 logarithm function
  • 8.155 LOG_GAMMA — Logarithm of the Gamma function
  • 8.156 LOGICAL — Convert to logical type
  • 8.157 LONG — Convert to integer type
  • 8.158 LSHIFT — Left shift bits
  • 8.159 LSTAT — Get file status
  • 8.160 LTIME — Convert time to local time info
  • 8.161 MALLOC — Allocate dynamic memory
  • 8.162 MASKL — Left justified mask
  • 8.163 MASKR — Right justified mask
  • 8.164 MATMUL — matrix multiplication
  • 8.165 MAX — Maximum value of an argument list
  • 8.166 MAXEXPONENT — Maximum exponent of a real kind
  • 8.167 MAXLOC — Location of the maximum value within an array
  • 8.168 MAXVAL — Maximum value of an array
  • 8.169 MCLOCK — Time function
  • 8.170 MCLOCK8 — Time function (64-bit)
  • 8.171 MERGE — Merge variables
  • 8.172 MERGE_BITS — Merge of bits under mask
  • 8.173 MIN — Minimum value of an argument list
  • 8.174 MINEXPONENT — Minimum exponent of a real kind
  • 8.175 MINLOC — Location of the minimum value within an array
  • 8.176 MINVAL — Minimum value of an array
  • 8.177 MOD — Remainder function
  • 8.178 MODULO — Modulo function
  • 8.179 MOVE_ALLOC — Move allocation from one object to another
  • 8.180 MVBITS — Move bits from one integer to another
  • 8.181 NEAREST — Nearest representable number
  • 8.182 NEW_LINE — New line character
  • 8.183 NINT — Nearest whole number
  • 8.184 NORM2 — Euclidean vector norms
  • 8.185 NOT — Logical negation
  • 8.186 NULL — Function that returns an disassociated pointer
  • 8.187 NUM_IMAGES — Function that returns the number of images
  • 8.188 OR — Bitwise logical OR
  • 8.189 PACK — Pack an array into an array of rank one
  • 8.190 PARITY — Reduction with exclusive OR
  • 8.191 PERROR — Print system error message
  • 8.192 POPCNT — Number of bits set
  • 8.193 POPPAR — Parity of the number of bits set
  • 8.194 PRECISION — Decimal precision of a real kind
  • 8.195 PRESENT — Determine whether an optional dummy argument is specified
  • 8.196 PRODUCT — Product of array elements
  • 8.197 RADIX — Base of a model number
  • 8.198 RAN — Real pseudo-random number
  • 8.199 RAND — Real pseudo-random number
  • 8.200 RANDOM_NUMBER — Pseudo-random number
  • 8.201 RANDOM_SEED — Initialize a pseudo-random number sequence
  • 8.202 RANGE — Decimal exponent range
  • 8.203 RANK — Rank of a data object
  • 8.204 REAL — Convert to real type
  • 8.205 RENAME — Rename a file
  • 8.206 REPEAT — Repeated string concatenation
  • 8.207 RESHAPE — Function to reshape an array
  • 8.208 RRSPACING — Reciprocal of the relative spacing
  • 8.209 RSHIFT — Right shift bits
  • 8.210 SAME_TYPE_AS — Query dynamic types for equality
  • 8.211 SCALE — Scale a real value
  • 8.212 SCAN — Scan a string for the presence of a set of characters
  • 8.213 SECNDS — Time function
  • 8.214 SECOND — CPU time function
  • 8.215 SELECTED_CHAR_KIND — Choose character kind
  • 8.216 SELECTED_INT_KIND — Choose integer kind
  • 8.217 SELECTED_REAL_KIND — Choose real kind
  • 8.218 SET_EXPONENT — Set the exponent of the model
  • 8.219 SHAPE — Determine the shape of an array
  • 8.220 SHIFTA — Right shift with fill
  • 8.221 SHIFTL — Left shift
  • 8.222 SHIFTR — Right shift
  • 8.223 SIGN — Sign copying function
  • 8.224 SIGNAL — Signal handling subroutine (or function)
  • 8.225 SIN — Sine function
  • 8.226 SINH — Hyperbolic sine function
  • 8.227 SIZE — Determine the size of an array
  • 8.228 SIZEOF — Size in bytes of an expression
  • 8.229 SLEEP — Sleep for the specified number of seconds
  • 8.230 SPACING — Smallest distance between two numbers of a given type
  • 8.231 SPREAD — Add a dimension to an array
  • 8.232 SQRT — Square-root function
  • 8.233 SRAND — Reinitialize the random number generator
  • 8.234 STAT — Get file status
  • 8.235 STORAGE_SIZE — Storage size in bits
  • 8.236 SUM — Sum of array elements
  • 8.237 SYMLNK — Create a symbolic link
  • 8.238 SYSTEM — Execute a shell command
  • 8.239 SYSTEM_CLOCK — Time function
  • 8.240 TAN — Tangent function
  • 8.241 TANH — Hyperbolic tangent function
  • 8.242 THIS_IMAGE — Function that returns the cosubscript index of this image
  • 8.243 TIME — Time function
  • 8.244 TIME8 — Time function (64-bit)
  • 8.245 TINY — Smallest positive number of a real kind
  • 8.246 TRAILZ — Number of trailing zero bits of an integer
  • 8.247 TRANSFER — Transfer bit patterns
  • 8.248 TRANSPOSE — Transpose an array of rank two
  • 8.249 TRIM — Remove trailing blank characters of a string
  • 8.250 TTYNAM — Get the name of a terminal device.
  • 8.251 UBOUND — Upper dimension bounds of an array
  • 8.252 UCOBOUND — Upper codimension bounds of an array
  • 8.253 UMASK — Set the file creation mask
  • 8.254 UNLINK — Remove a file from the file system
  • 8.255 UNPACK — Unpack an array of rank one into an array
  • 8.256 VERIFY — Scan a string for characters not a given set
  • 8.257 XOR — Bitwise logical exclusive OR
• 9 Intrinsic Modules
  • 9.1 ISO_FORTRAN_ENV
  • 9.2 ISO_C_BINDING
  • 9.3 OpenMP Modules OMP_LIB and OMP_LIB_KINDS
• Contributing
  • Contributors to GNU Fortran
  • Projects
  • Proposed Extensions
    • Compiler extensions:
    • Environment Options
• GNU General Public License
• GNU Free Documentation License
  • ADDENDUM: How to use this License for your documents
• Funding Free Software
• Option Index
• Keyword Index