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<title>16.4 File access</title>
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<a name="1204573"> </a><font color="#003366" face="Verdana, Arial, Helvetica, sans-serif">16.4 File access</font>
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<p>
<a name="1204575"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The application can read and write host files. A file is opened using <font size=2 face=Courier><strong>debugopen</strong></font>, which takes the standard ANSI file mode string, as used by <font size=2 face=Courier><strong>fopen</strong></font>, to define the type of file. The function returns the integer file descriptor, which must be used for subsequent reads, writes and to close the file. If an error occurs then <font size=2 face=Courier><strong>-1</strong></font> is returned. The following code opens an output file named <font size=2 face=Courier><strong>testout.dat</strong></font> in binary mode:</font>
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<a name="1204576"> </a><font size=2 face=Courier><strong>#define ERROR -1<br><br></strong></font>
<a name="1204578"> </a><font size=2 face=Courier><strong>long int outfile;<br><br></strong></font>
<a name="1204580"> </a><font size=2 face=Courier><strong>outfile = debugopen("testout.dat", "wb");<br>if (outfile == ERROR) debugmessage ("Can't open testout.dat");<br></strong></font>
<p>
<a name="1204582"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">Similarly, the following code opens an input file named <font size=2 face=Courier><strong>testin.dat</strong></font>:</font>
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<a name="1204583"> </a><font size=2 face=Courier><strong>#define ERROR -1<br><br></strong></font>
<a name="1204585"> </a><font size=2 face=Courier><strong>long int infile;<br><br></strong></font>
<a name="1204587"> </a><font size=2 face=Courier><strong>infile = debugopen("testin.dat", "r");<br>if (infile == ERROR) debugmessage ("Can't open testin.dat");<br></strong></font>
<p>
<a name="1204589"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">An output file can be written to using <font size=2 face=Courier><strong>debugwrite</strong></font>. This takes the number of bytes to be written as a parameter and returns the actual number of bytes written, or <font size=2 face=Courier><strong>0</strong></font> if there is an error.</font>
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<a name="1204590"> </a><font size=2 face=Courier><strong>char *test_string = "Hello World";<br>long int num_bytes_written;<br>num_bytes_written =<br>⌨️ 快捷键说明
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