NAG FL Interface
x04acf (open)

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1 Purpose

x04acf opens a Fortran unit number for reading, writing or appending, and associates the unit with a named file.

2 Specification

Fortran Interface
Subroutine x04acf ( iounit, file, mode, ifail)
Integer, Intent (In) :: iounit, mode
Integer, Intent (Inout) :: ifail
Character (*), Intent (In) :: file
C Header Interface
#include <nag.h>
void  x04acf_ (const Integer *iounit, const char *file, const Integer *mode, Integer *ifail, const Charlen length_file)
The routine may be called by the names x04acf or nagf_file_open.

3 Description

x04acf is especially useful if the calling language is not Fortran. It opens a Fortran unit number for reading, writing or appending, and associates the unit with a filename specified by the argument file.

4 References

None.

5 Arguments

1: iounit Integer Input
On entry: the Fortran unit number which identifies the file to be read from, written to or appended to. Note that this may be system dependent. Values in the range 7 to 1000 should however be safe on most systems.
2: file Character(*) Input
On entry: the name of the file to be opened.
Constraint: must contain a valid filename for the computer system being used.
3: mode Integer Input
On entry: specifies whether the file is to be opened for reading, writing or appending.
mode=0
The file is to be opened for reading.
mode=1
The file is to be opened for writing.
mode=2
The file is to be opened for appending.
Constraint: 0mode2.
4: ifail Integer Input/Output
On entry: ifail must be set to 0, −1 or 1 to set behaviour on detection of an error; these values have no effect when no error is detected.
A value of 0 causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of −1 means that an error message is printed while a value of 1 means that it is not.
If halting is not appropriate, the value −1 or 1 is recommended. If message printing is undesirable, then the value 1 is recommended. Otherwise, the value 0 is recommended. When the value -1 or 1 is used it is essential to test the value of ifail on exit.
On exit: ifail=0 unless the routine detects an error or a warning has been flagged (see Section 6).

6 Error Indicators and Warnings

If on entry ifail=0 or −1, explanatory error messages are output on the current error message unit (as defined by x04aaf).
Errors or warnings detected by the routine:
ifail=1
On entry, mode=value.
Constraint: 0mode2.
ifail=2
Cannot open file value for reading on channel value.
ifail=3
Cannot open file value for writing on channel value.
ifail=4
Cannot open file value for appending on channel value.
ifail=-99
An unexpected error has been triggered by this routine. Please contact NAG.
See Section 7 in the Introduction to the NAG Library FL Interface for further information.
ifail=-399
Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library FL Interface for further information.
ifail=-999
Dynamic memory allocation failed.
See Section 9 in the Introduction to the NAG Library FL Interface for further information.

7 Accuracy

Not applicable.

8 Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.
x04acf is not threaded in any implementation.

9 Further Comments

None.

10 Example

This example illustrates how to open a file for writing.

10.1 Program Text

Program Text (x04acfe.f90)

10.2 Program Data

None.

10.3 Program Results

Program Results (x04acfe.r)