fortran inquire的用法
Fortran is a high-level programming language that has been widely used in scientific and engineering applications since its development in the 1950s. One of the important features of Fortran is the "inquire" statement, which allows a programmer to obtain information about a file without actually opening it. In this article, we will explore the usage of Fortran's "inquire" statement in detail.
The "inquire" statement in Fortran is primarily used to retrieve information about a file, such as its existence, accessibility, size, and format. It serves as a useful tool for handling files and directories in a program, enabling the programmer to make informed decisions based on the status of the file.
To use the "inquire" statement, you must first open the necessary file using the "open" statement. The "open" statement is used to establish a connection between the program and the file, allowing the program to read from or write to it. Once the file is open, you can use the "inquire" statement to gather information about it.
The general syntax of the "inquire" statement is as follows:
inquire([inquire-spec-list])
The "inquire-spec-list" is a list of one or more "inquire-specs," which specify the information you want to retrieve about the file. The commonly used "inquire-specs" include "file," "exist," "opened," "number," "access," "sequential," "direct," "formatted," and "unformatted."
To illustrate the usage of the "inquire" statement, let's consider an example where we want to check the existence and size of a file named "" The program snippet below demonstrates the steps involved:
1. Declare the necessary variables:
character(255) :: filename        ! variable to hold the file name
logical :: file_exists            ! logical variable to store existence status
integer :: file_size              ! variable to store the size of the file
2. Obtain the file name from the user or specify it directly:
filename = ""
3. Open the file:
open(10, file=filename, status='old')
4. Use the "inquire" statement to check the existence and size of the file:
inquire(file=filename, exist=file_exists, size=file_size)
In this example, the "exist" specifier is used to determine whether the file exists. The result is stored in the logical variable "file_exists." Similarly, the "size" specifier is used to retrieve the size of the file, which is stored in the integer variable "file_size."
5. Process the file based on the obtained information:
if (file_exists) then
    write(*,*) "The file exists."
    write(*,*) "Size of the file:", file_size, "bytes."
    ! Additional processing can be done here
else
    write(*,*) "The file does not exist."
    ! Additional error handling can be done hereexists的用法
end if
In this step, the program checks the logical variable "file_exists" to determine if the file exists. If it does, the program proceeds with additional processing, such as reading or writing data. If the file does not exist, appropriate error handling can be implemented.
It is important to note that the "inquire" statement does not modify the file or change its attributes. It merely provides information about the file, which can be used for decision-making purposes within the program.
In conclusion, the "inquire" statement in Fortran is a powerful tool for obtaining information about files without actually opening them. It allows programmers to make informed decisions based on the status of the file, such as its existence and size. By using the "inquire" statement in conjunction with the "open" statement, programmers can effectively handle files and directories within their programs.

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