NAG Library Routine Document

x04acf (open)

1

Purpose

2

Specification

3

Description

4

References

5

Arguments

1:     $\mathbf{iounit}$ – IntegerInput

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:     $\mathbf{file}$ – 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:     $\mathbf{mode}$ – IntegerInput

On entry: specifies whether the file is to be opened for reading, writing or appending.

$\mathbf{mode}=0$

The file is to be opened for reading.

$\mathbf{mode}=1$

The file is to be opened for writing.

$\mathbf{mode}=2$

The file is to be opened for appending.

Constraint: $0\le \mathbf{mode}\le 2$.

4:     $\mathbf{ifail}$ – IntegerInput/Output

On entry: ifail must be set to $0$, $-1\text{ or }1$. If you are unfamiliar with this argument you should refer to Section 3.4 in How to Use the NAG Library and its Documentation for details.

For environments where it might be inappropriate to halt program execution when an error is detected, the value $-1\text{ or }1$ is recommended. If the output of error messages is undesirable, then the value $1$ is recommended. Otherwise, if you are not familiar with this argument, the recommended value is $0$. When the value $-\mathbf{1}\text{ or }\mathbf{1}$ is used it is essential to test the value of ifail on exit.

On exit: $\mathbf{ifail}=\mathbf{0}$ unless the routine detects an error or a warning has been flagged (see Section 6).

6

Error Indicators and Warnings

$\mathbf{ifail}=1$

On entry, $\mathbf{mode}=〈\mathit{\text{value}}〉$.
Constraint: $0\le \mathbf{mode}\le 2$.

$\mathbf{ifail}=2$

Cannot open file $〈\mathit{\text{value}}〉$ for reading on channel $〈\mathit{\text{value}}〉$.

$\mathbf{ifail}=3$

Cannot open file $〈\mathit{\text{value}}〉$ for writing on channel $〈\mathit{\text{value}}〉$.

$\mathbf{ifail}=4$

Cannot open file $〈\mathit{\text{value}}〉$ for appending on channel $〈\mathit{\text{value}}〉$.

$\mathbf{ifail}=-99$

An unexpected error has been triggered by this routine. Please contact NAG.

See Section 3.9 in How to Use the NAG Library and its Documentation for further information.

$\mathbf{ifail}=-399$

Your licence key may have expired or may not have been installed correctly.

See Section 3.8 in How to Use the NAG Library and its Documentation for further information.

$\mathbf{ifail}=-999$

Dynamic memory allocation failed.

See Section 3.7 in How to Use the NAG Library and its Documentation for further information.

7

Accuracy

8

Parallelism and Performance

9

Further Comments

10

Example

10.1

Program Text

Program Text (x04acfe.f90)

10.2

Program Data

10.3

Program Results

Program Results (x04acfe.r)