Fortran 简明教程
Fortran - File Input Output
Fortran 允许您从文件中读取数据和写入数据。
Fortran allows you to read data from, and write data into files.
在上一章中，你已经看到了如何从终端读取数据以及将数据写入终端。在本章中，你将学习 Fortran 提供的文件输入和输出功能。
In the last chapter, you have seen how to read data from, and write data to the terminal. In this chapter you will study file input and output functionalities provided by Fortran.
你可以读写一个或多个文件。OPEN、WRITE、READ 和 CLOSE 语句允许你实现这一点。
You can read and write to one or more files. The OPEN, WRITE, READ and CLOSE statements allow you to achieve this.
Opening and Closing Files
在使用文件之前，你必须打开该文件。 open 命令用于打开文件以进行读或写。该命令的最简单形式为：
Before using a file you must open the file. The open command is used to open files for reading or writing. The simplest form of the command is −
open (unit = number, file = "name").但是，open 语句的通用形式可能为：
However, the open statement may have a general form −
open (list-of-specifiers)下表描述了最常用的说明符：
The following table describes the most commonly used specifiers −
Sr.No |
Specifier & Description |
1 |
[UNIT=] u The unit number u could be any number in the range 9-99 and it indicates the file, you may choose any number but every open file in the program must have a unique number |
2 |
IOSTAT= ios It is the I/O status identifier and should be an integer variable. If the open statement is successful then the ios value returned is zero else a non-zero value. |
3 |
ERR = err It is a label to which the control jumps in case of any error. |
4 |
FILE = fname File name, a character string. |
5 |
STATUS = sta It shows the prior status of the file. A character string and can have one of the three values NEW, OLD or SCRATCH. A scratch file is created and deleted when closed or the program ends. |
6 |
ACCESS = acc It is the file access mode. Can have either of the two values, SEQUENTIAL or DIRECT. The default is SEQUENTIAL. |
7 |
FORM = frm It gives the formatting status of the file. Can have either of the two values FORMATTED or UNFORMATTED. The default is UNFORMATTED |
8 |
RECL = rl It specifies the length of each record in a direct access file. |
打开文件后，通过阅读和写入语句来访问它。完成后，应该使用 close 语句关闭它。
After the file has been opened, it is accessed by read and write statements. Once done, it should be closed using the close statement.
close 语句具有以下语法：
The close statement has the following syntax −
close ([UNIT = ]u[,IOSTAT = ios,ERR = err,STATUS = sta])请注意，括号中的参数是可选的。
Please note that the parameters in brackets are optional.
Example
此示例演示如何打开一个新文件以将一些数据写入文件中。
This example demonstrates opening a new file for writing some data into the file.
program outputdata
implicit none
real, dimension(100) :: x, y
real, dimension(100) :: p, q
integer :: i
! data
do i=1,100
x(i) = i * 0.1
y(i) = sin(x(i)) * (1-cos(x(i)/3.0))
end do
! output data into a file
open(1, file = 'data1.dat', status = 'new')
do i=1,100
write(1,*) x(i), y(i)
end do
close(1)
end program outputdata当编译并执行上述代码时，它将创建文件 data1.dat，并将 x 和 y 数组值写入其中。然后关闭文件。
When the above code is compiled and executed, it creates the file data1.dat and writes the x and y array values into it. And then closes the file.
Reading from and Writing into the File
读取和写入语句分别用于从文件中读取和写入文件。
The read and write statements respectively are used for reading from and writing into a file respectively.
它们具有以下语法 −
They have the following syntax −
read ([UNIT = ]u, [FMT = ]fmt, IOSTAT = ios, ERR = err, END = s)
write([UNIT = ]u, [FMT = ]fmt, IOSTAT = ios, ERR = err, END = s)大多数规范符已在上面的表格中进行讨论。
Most of the specifiers have already been discussed in the above table.
END = s 规范符是一个语句标签，当程序达到文件结尾时，程序跳转到该标签。
The END = s specifier is a statement label where the program jumps, when it reaches end-of-file.
Example
此示例演示了从文件中读取和写入文件。
This example demonstrates reading from and writing into a file.
在这个程序中，我们从上个示例中创建的文件 data1.dat 中读取数据，并在屏幕上显示它。
In this program we read from the file, we created in the last example, data1.dat, and display it on screen.
program outputdata
implicit none
real, dimension(100) :: x, y
real, dimension(100) :: p, q
integer :: i
! data
do i = 1,100
x(i) = i * 0.1
y(i) = sin(x(i)) * (1-cos(x(i)/3.0))
end do
! output data into a file
open(1, file = 'data1.dat', status='new')
do i = 1,100
write(1,*) x(i), y(i)
end do
close(1)
! opening the file for reading
open (2, file = 'data1.dat', status = 'old')
do i = 1,100
read(2,*) p(i), q(i)
end do
close(2)
do i = 1,100
write(*,*) p(i), q(i)
end do
end program outputdata编译并执行上述代码后，将产生以下结果 −
When the above code is compiled and executed, it produces the following result −
0.100000001 5.54589933E-05
0.200000003 4.41325130E-04
0.300000012 1.47636665E-03
0.400000006 3.45637114E-03
0.500000000 6.64328877E-03
0.600000024 1.12552457E-02
0.699999988 1.74576249E-02
0.800000012 2.53552198E-02
0.900000036 3.49861123E-02
1.00000000 4.63171229E-02
1.10000002 5.92407547E-02
1.20000005 7.35742599E-02
1.30000007 8.90605897E-02
1.39999998 0.105371222
1.50000000 0.122110792
1.60000002 0.138823599
1.70000005 0.155002072
1.80000007 0.170096487
1.89999998 0.183526158
2.00000000 0.194692180
2.10000014 0.202990443
2.20000005 0.207826138
2.29999995 0.208628103
2.40000010 0.204863414
2.50000000 0.196052119
2.60000014 0.181780845
2.70000005 0.161716297
2.79999995 0.135617107
2.90000010 0.103344671
3.00000000 6.48725405E-02
3.10000014 2.02930309E-02
3.20000005 -3.01767997E-02
3.29999995 -8.61928314E-02
3.40000010 -0.147283033
3.50000000 -0.212848678
3.60000014 -0.282169819
3.70000005 -0.354410470
3.79999995 -0.428629100
3.90000010 -0.503789663
4.00000000 -0.578774154
4.09999990 -0.652400017
4.20000029 -0.723436713
4.30000019 -0.790623367
4.40000010 -0.852691114
4.50000000 -0.908382416
4.59999990 -0.956472993
4.70000029 -0.995793998
4.80000019 -1.02525222
4.90000010 -1.04385209
5.00000000 -1.05071592
5.09999990 -1.04510069
5.20000029 -1.02641726
5.30000019 -0.994243503
5.40000010 -0.948338211
5.50000000 -0.888650239
5.59999990 -0.815326691
5.70000029 -0.728716135
5.80000019 -0.629372001
5.90000010 -0.518047631
6.00000000 -0.395693362
6.09999990 -0.263447165
6.20000029 -0.122622721
6.30000019 2.53026206E-02
6.40000010 0.178709000
6.50000000 0.335851669
6.59999990 0.494883657
6.70000029 0.653881252
6.80000019 0.810866773
6.90000010 0.963840425
7.00000000 1.11080539
7.09999990 1.24979746
7.20000029 1.37891412
7.30000019 1.49633956
7.40000010 1.60037732
7.50000000 1.68947268
7.59999990 1.76223695
7.70000029 1.81747139
7.80000019 1.85418403
7.90000010 1.87160957
8.00000000 1.86922085
8.10000038 1.84674001
8.19999981 1.80414569
8.30000019 1.74167395
8.40000057 1.65982044
8.50000000 1.55933595
8.60000038 1.44121361
8.69999981 1.30668485
8.80000019 1.15719533
8.90000057 0.994394958
9.00000000 0.820112705
9.10000038 0.636327863
9.19999981 0.445154816
9.30000019 0.248800844
9.40000057 4.95488606E-02
9.50000000 -0.150278628
9.60000038 -0.348357052
9.69999981 -0.542378068
9.80000019 -0.730095863
9.90000057 -0.909344316
10.0000000 -1.07807255