📅 最后修改于: 2020-11-04 06:19:32 🧑 作者: Mango
Fortran允许您从文件读取数据并将数据写入文件。
在上一章中，您已经了解了如何从终端读取数据以及如何向终端写入数据。在本章中，您将研究Fortran提供的文件输入和输出功能。
您可以读写一个或多个文件。 OPEN，WRITE，READ和CLOSE语句使您可以实现这一点。
使用文件之前，您必须打开文件。 open命令用于打开文件以进行读取或写入。该命令的最简单形式是-
open (unit = number, file = "name").
但是，开放式声明可能具有一般形式-
open (list-of-specifiers)
下表描述了最常用的说明符-
| 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，可通过读写语句对其进行访问。完成后，应使用close语句将其关闭。
close语句具有以下语法-
close ([UNIT = ]u[,IOSTAT = ios,ERR = err,STATUS = sta])
请注意，方括号中的参数是可选的。
例
本示例演示打开一个新文件以将一些数据写入该文件。
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
编译并执行上述代码后，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。
读取和写入语句分别用于分别读取和写入文件。
它们具有以下语法-
read ([UNIT = ]u, [FMT = ]fmt, IOSTAT = ios, ERR = err, END = s)
write([UNIT = ]u, [FMT = ]fmt, IOSTAT = ios, ERR = err, END = s)
上表已讨论了大多数说明符。
END = s说明符是程序到达文件末尾时在其中跳转的语句标签。
例
本示例演示了从文件读取和写入文件。
在该程序中，我们从上一个示例中创建的文件data1.dat中读取文件，并将其显示在屏幕上。
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-
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