XL Fortran for AIX 8.1
Language Reference
Purpose
The WRITE statement is a data transfer output statement.
Format
>>-WRITE--(--io_control_list--)--+------------------+----------><
'-output_item_list-'
|
- output_item
- is an output list item. An output list specifies the data to be
transferred. An output list item can be:
- A variable name. An array is treated as if all of its elements were
specified in the order in which they are arranged in storage.
A pointer must be associated with a target, and an allocatable object must be allocated. A derived-type object cannot have any
ultimate component that is outside the scoping unit of this statement.
The evaluation of output_item cannot result in a derived-type object
that contains a pointer. The structure components of a structure in a
formatted statement are treated as if they appear in the order of the
derived-type definition; in an unformatted statement, the structure
components are treated as a single value in their internal representation
(including padding).
- An expression
- An implied-DO list, as described under Implied-DO List
- io_control
- is a list that must contain one unit specifier (UNIT=), and can
also contain one of each of the other valid specifiers:
- [UNIT=] u
- is a unit specifier that specifies the unit to be used in the output
operation. u is an external unit identifier or internal file
identifier.
+-------------------------------IBM Extension--------------------------------+
An external unit identifier refers to an external file. It is one of
the following:
- An integer expression whose value is in the range 0 through
2,147,483,647.
- An asterisk, which identifies external unit 6 and is preconnected to
standard output.
+----------------------------End of IBM Extension----------------------------+
An internal file identifier refers to an internal file. It is the
name of a character variable, which cannot be an array section with a vector
subscript.
If the optional characters UNIT= are omitted, u must be
the first item in io_control_list. If UNIT= is
specified, FMT= must also be specified.
- [FMT=] format
- is a format specifier that specifies the format to be used in the output
operation. format is a format identifier that can be:
- The statement label of a FORMAT statement. The
FORMAT statement must be in the same scoping unit.
- The name of a scalar INTEGER(4) or INTEGER(8) variable
that was assigned the statement label of a FORMAT statement.
The FORMAT statement must be in the same scoping unit.
+---------------------------------Fortran 95---------------------------------+
Fortran 95 does not permit assigning of a statement
label.
+-----------------------------End of Fortran 95------------------------------+
- A character constant enclosed in parentheses. Only the format codes
listed under FORMAT can be used between the parentheses. Blank characters
can precede the left parenthesis or follow the right parenthesis.
- A character variable that contains character data whose leftmost character
positions constitute a valid format. A valid format begins with a left
parenthesis and ends with a right parenthesis. Only the format codes
described in the FORMAT statement can be used between the
parentheses. Blank characters can precede the left parenthesis or
follow the right parenthesis. If format is an array element,
the format identifier must not exceed the length of the array element.
- An array of noncharacter intrinsic type. The data must be a valid
format identifier as described under character array.
- Any character expression, except one involving concatenation of an operand
that specifies inherited length, unless the operand is the name of a
constant.
- An asterisk, specifying list-directed formatting.
- A namelist specifier that specifies the name
of a namelist list that you have previously defined.
If the optional characters FMT= are omitted, format must
be the second item in io_control_list, and the first item must be the
unit specifier with UNIT= omitted. NML= and
FMT= cannot both be specified in the same output statement.
- REC= integer_expr
- is a record specifier that specifies the number of the record to be
written in a file connected for direct access. The REC=
specifier is only permitted for direct output. integer_expr is
an integer expression whose value is positive. A record specifier is
not valid if formatting is list-directed or if the unit specifier specifies an
internal file. The record specifier represents the relative position of
a record within a file. The relative position number of the first
record is 1.
- IOSTAT= ios
- is an input/output status specifier that specifies the status of the
input/output operation. ios is a scalar variable of type
INTEGER(4) or default integer. Coding the IOSTAT=
specifier suppresses error messages. When the statement finishes
execution, ios is defined with:
- A zero value if no error condition occurs
- A positive value if an error occurs.
+-------------------------------IBM Extension--------------------------------+
- ID= integer_variable
- indicates that the data transfer is to be done asynchronously. The
integer_variable is a scalar of type INTEGER(4) or default
integer. If no error is encountered, the integer_variable is
defined with a value after executing the asynchronous data transfer
statement. This value must be used in the matching WAIT
statement.
Asynchronous data transfer must either be direct unformatted or sequential
unformatted. Asynchronous I/O to internal files is prohibited.
Asynchronous I/O to raw character devices (for example, tapes or raw logical
volumes) is prohibited. The integer_variable must not be
associated with any entity in the data transfer I/O list, or with a
do_variable of an io_implied_do in the data transfer I/O
list. If the integer_variable is an array element reference,
its subscript values must not be affected by the data transfer, the
io_implied_do processing, or the definition or evaluation of any
other specifier in the io_control_spec.
+----------------------------End of IBM Extension----------------------------+
- ERR= stmt_label
- is an error specifier that specifies the statement label of an executable
statement in the same scoping unit to which control is to transfer in the case
of an error. Coding the ERR= specifier suppresses error
messages.
+-------------------------------IBM Extension--------------------------------+
- NUM= integer_variable
- is a number specifier that specifies the number of bytes of data
transmitted between the I/O list and the file.
integer_variable is a variable name of type INTEGER(4), type
INTEGER(8) in 64-bit, or type default integer. The
NUM= specifier is only permitted for unformatted output.
Coding the NUM parameter suppresses the indication of an error that
would occur if the number of bytes represented by the output list is greater
than the number of bytes that can be written into the record. In this
case, integer_variable is set to a value that is the maximum length
record that can be written. Data from remaining output list items is
not written into subsequent records. In the portion of the program that
executes between the asynchronous data transfer statement and the matching
WAIT statement, the integer_variable in the NUM=
specifier or any variable associated with it must not be referenced, become
defined, or become undefined.
+----------------------------End of IBM Extension----------------------------+
- [NML=] name
- is a namelist specifier that specifies the name of a
namelist list that you have previously defined. If the optional
characters NML= are not specified, the namelist name must appear as
the second parameter in the list, and the first item must be the unit
specifier with UNIT= omitted. If both NML= and
UNIT= are specified, all the parameters can appear in any
order. The NML= specifier is an alternative to
FMT=. Both NML= and FMT= cannot be specified
in the same output statement.
- ADVANCE= char_expr
- is an advance specifier that determines whether nonadvancing output occurs
for this statement. char_expr is a character expression that
must evaluate to YES or NO. If NO is
specified, nonadvancing output occurs. If YES is specified,
advancing, formatted sequential output occurs. The default value is
YES. ADVANCE= can be specified only in a formatted
sequential WRITE statement with an explicit format specification that
does not specify an internal file unit specifier.
>>-(--do_object_list-- , --------------------------------------->
>--do_variable = arith_expr1, arith_expr2----------------------->
>--+---+--+-------------+--)-----------------------------------><
'-,-' '-arith_expr3-'
|
- do_object
- is an output list item
- do_variable
- is a named scalar variable of type integer or real
- arith_expr1, arith_expr2, and
arith_expr3
- are scalar numeric expressions
The range of an implied-DO list is the list
do_object_list. The iteration count and values of the
DO variable are established from arith_expr1,
arith_expr2, and arith_expr3, the same as for a DO
statement. When the implied-DO list is executed, the items in
the do_object_list are specified once for each iteration of the
implied-DO list, with the appropriate substitution of values for any
occurrence of the DO variable.
Rules
+-------------------------------IBM Extension--------------------------------+
If a NUM= specifier is present, neither a format specifier
nor a namelist specifier can be present.
+----------------------------End of IBM Extension----------------------------+
Variables specified for the IOSTAT= and NUM= specifiers
must not be associated with any output list item, namelist list item, or
DO variable of an implied-DO list. If such a
specifier variable is an array element, its subscript values must not be
affected by the data transfer, any implied-DO processing, or the
definition or evaluation of any other specifier.
If the ERR= and IOSTAT= specifiers are set and an error
is encountered during a synchronous data transfer, transfer is made to the
statement specified by the ERR= specifier and a positive integer
value is assigned to ios.
+-------------------------------IBM Extension--------------------------------+
If the ERR= or IOSTAT= specifiers are set and an
error is encountered during an asynchronous data transfer, execution of the
matching WAIT statement is not required.
If a conversion error is encountered and the CNVERR
run-time option is set to NO, ERR= is not branched to,
although IOSTAT= may be set.
If IOSTAT= and ERR= are not specified,
- The program stops if a severe error is encountered.
- The program continues to the next statement if a recoverable error is
encountered and the ERR_RECOVERY run-time option is set to
YES. If the option is set to NO, the program
stops.
- The program continues to the next statement when a conversion error is
encountered if the ERR_RECOVERY run-time option is set to
YES. If the CNVERR run-time option is set to
YES, conversion errors are treated as recoverable errors; when
CNVERR=NO, they are treated as conversion errors.
+----------------------------End of IBM Extension----------------------------+
PRINT format has the same effect as
WRITE(*,format).
Examples
WRITE (6,FMT='(10F8.2)') (LOG(A(I)),I=1,N+9,K),G
Related Information
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