The OPEN statement connects an external file to a unit, creates a new file and connects it to a unit, creates a preconnected file, or changes certain properties of a connection.
The OPEN statement takes the following form:
The OPEN specifiers and their acceptable values are summarized in Table 13-1.
The OPEN specifiers are described individually in the following sections. The control specifiers that can be specified in an OPEN statement (UNIT, ERR, and IOSTAT) are discussed in Section 10.2.1.
Table 13-1 OPEN Statement Specifiers and Values on Tru64 UNIX, Linux, and Windows Systems
| Specifier | Values | Function | Default |
|---|---|---|---|
| ACCESS | 'SEQUENTIAL'
'DIRECT' 'APPEND' | Access mode | 'SEQUENTIAL' |
| ACTION
(or MODE 1) |
'READ'
'WRITE' 'READWRITE' |
File access | 'READWRITE' |
| ASSOCIATEVARIABLE | var | Next direct access record | No default |
| BLANK | 'NULL'
'ZERO' | Interpretation of blanks | 'NULL' |
| BLOCKSIZE | n_expr | Physical block size | Filesystem default |
| BUFFERCOUNT | n_expr | Number of I/O buffers | One |
| BUFFERED | 'YES'
'NO' |
Buffering for WRITE operations | 'NO' |
| CARRIAGECONTROL | 'FORTRAN'
'LIST' 'NONE' |
Print control |
Formatted: 'LIST' 2
Unformatted: 'NONE' |
| CONVERT | 'LITTLE_ENDIAN'
'BIG_ENDIAN' 'CRAY' 'FDX' 'FGX' 'IBM' 'VAXD' 'VAXG' 'NATIVE' |
Numeric format specification | 'NATIVE' |
| DEFAULTFILE | c_expr | Default file pathname | Current working directory |
| DELIM | 'APOSTROPHE'
'QUOTE' 'NONE' | Delimiter for character constants | 'NONE' |
| DISPOSE
(or DISP) |
'KEEP' or 'SAVE'
'DELETE' 'PRINT' 'PRINT/DELETE' 'SUBMIT' 'SUBMIT/DELETE' |
File disposition at close | 'KEEP' |
| ERR | label | Error transfer control | No default |
| FILE
(or NAME) |
c_expr | File pathname (file name) | fort.n 3 |
| FORM | 'FORMATTED'
'UNFORMATTED' 'BINARY' 1 | Format type | Depends on ACCESS setting |
| IOFOCUS1 | .TRUE. .FALSE. | Active window in QuickWin application | .TRUE. 4 |
| IOSTAT | var | I/O status | No default |
| MAXREC | n_expr | Direct access record limit | No limit |
| ORGANIZATION |
'SEQUENTIAL'
'RELATIVE' |
File organization | 'SEQUENTIAL' |
| PAD | 'YES'
'NO' | Record padding | 'YES' |
| POSITION | 'ASIS'
'REWIND' 'APPEND' | File positioning | 'ASIS' |
| READONLY | No value | Write protection | No default |
| RECL
(or RECORDSIZE) | n_expr | Record length | Depends on RECORDTYPE, ORGANIZATION, and FORM settings 5 |
| RECORDTYPE | 'FIXED'
'VARIABLE' 'SEGMENTED' 'STREAM' 'STREAM_CR' 'STREAM_LF' |
Record type | Depends on ORGANIZATION, CARRIAGECONTROL, ACCESS, and FORM settings |
| SHARE 1,6 | 'DENYRW'
'DENYWR' 'DENYRD' 'DENYNONE' |
File locking | 'DENYWR' |
| SHARED 6 | No value | File sharing allowed | U*X: SHARED
WNT AND W9*: No default |
| STATUS (or TYPE) | 'OLD'
'NEW' 'SCRATCH' 'REPLACE' 'UNKNOWN' |
File status at open | 'UNKNOWN' 7 |
| TITLE 1 | c_expr | Title for child window in QuickWin application | No default |
| UNIT | n_expr | Logical unit number | No default; an io-unit must be specified |
| USEROPEN | func | User program option | No default |
|
1 WNT, W9*
2 If you use the compiler option specifying OpenVMS defaults, and the unit is connected to a terminal, the default is 'FORTRAN'. 3 n is the unit number. 4 If you specify unit '*' the default is .FALSE.. 5 On Tru64 UNIX and Linux systems, the default depends only on the FORM setting. 6 For information on file sharing, see your user manual or programmer's guide. 7 The default differs under certain conditions (see Section 13.6.28). | |||
Key to Values
| |||
The control specifiers ([UNIT=]io-unit, ERR=label, and IOSTAT=i-var) and OPEN specifiers can appear anywhere within the parentheses following OPEN. However, if the UNIT keyword is omitted, the io-unit must appear first in the list.
Specifier values that are scalar numeric expressions can be any integer or real expression. The value of the expression is converted to integer data type before it is used in the OPEN statement.
Only one unit at a time can be connected to a file, but multiple OPENs can be performed on the same unit. If an OPEN statement is executed for a unit that already exists, the following occurs:
If the file names are the same, the values for the BLANK, CARRIAGECONTROL, CONVERT, DELIM, DISPOSE, ERR, IOSTAT, and PAD specifiers can be changed. Other OPEN specifier values cannot be changed, and the file position is unaffected.
The ERR and IOSTAT specifiers from any previously executed OPEN statement have no effect on any currently executing OPEN statement. If an error occurs, no file is opened or created.
Secondary operating system messages do not display when IOSTAT is specified. To display these messages, remove IOSTAT or use a platform-specific method. (For more information, see your user manual or programmer's guide.)
Examples
You can specify character values at run time by substituting a character expression for a specifier value in the OPEN statement. The character value can contain trailing blanks but not leading or embedded blanks; for example:
CHARACTER*6 FINAL /' '/
...
IF (expr) FINAL = 'DELETE'
OPEN (UNIT=1, STATUS='NEW', DISP=FINAL)
OPEN (UNIT=1, STATUS='NEW', ERR=100)
OPEN (UNIT=I, FILE='/dev/rmt8', &
STATUS='NEW', ERR=14, RECL=1024)
The following statement opens the file (created in the previous example) for input:
OPEN (UNIT=I, FILE='/dev/rmt8', READONLY, STATUS='OLD', &
RECL=1024)
The following example opens the existing file /usr/users/someone/test.dat:
OPEN (unit=10, DEFAULTFILE='/usr/users/someone/', FILE='test.dat',
1 FORM='FORMATTED', STATUS='OLD')
For More Information: