Obtaining File Information: INQUIRE Statement

The INQUIRE statement returns information about a file and has three forms:

Inquiry by Unit

An inquiry by unit is usually done for an opened (connected) file. An inquiry by unit causes the Intel Fortran RTL to check whether the specified unit is connected or not. One of the following occurs, depending on whether the unit is connected or not:

If the unit is connected:

If the unit is not connected:

For example, the following INQUIRE statement shows whether unit 3 has a file connected (OPENED specifier) in logical variable I_OPENED, the name (case-sensitive) in character variable I_NAME, and whether the file is opened for READ, WRITE, or READWRITE access in character variable I_ACTION:

INQUIRE (3, OPENED=I_OPENED, NAME=I_NAME, ACTION=I_ACTION)

Inquiry by File Name

An inquiry by name causes the Intel Fortran RTL to scan its list of open files for a matching file name. One of the following occurs, depending on whether a match occurs or not:

If a match occurs:

If no match occurs:

The following INQUIRE statement returns whether the file named log_file is connected in logical variable I_OPEN, whether the file exists in logical variable I_EXIST, and the unit number in integer variable I_NUMBER:

INQUIRE (FILE='log_file', OPENED=I_OPEN, EXIST=I_EXIST, NUMBER=I_NUMBER)

Inquiry by Output Item List

Unlike inquiry by unit or inquiry by name, inquiry by output item list does not attempt to access any external file. It returns the length of a record for a list of variables that would be used for unformatted WRITE, READ, and REWRITE statements. The following INQUIRE statement returns the maximum record length of the variable list in variable I_RECLENGTH. This variable is then used to specify the RECL value in the OPEN statement:

INQUIRE (IOLENGTH=I_RECLENGTH) A, B, H

OPEN (FILE='test.dat', FORM='UNFORMATTED', RECL=I_RECLENGTH, UNIT=9)

For an unformatted file, the IOLENGTH value is returned using 4-byte units, unless you specify the -assume byterecl option to request 1-byte units.