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70 lines
1.9 KiB
Plaintext
70 lines
1.9 KiB
Plaintext
NAME
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files - return a file or the maximum number of open files
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SYNOPSIS
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files([fnum])
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TYPES
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fnum int
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return files, int or null
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DESCRIPTION
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This function, then given the argument fnum, will use it as an
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index into an internal table of open file and return a file value.
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If that entry in the table is not in use, then the null value is
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returned instead. When no args are given, the maximum number of
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open files is returned.
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If you overwrite a variable containing a file value or don't save the
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result of an 'fopen', the opened file still remains open. Such 'lost'
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files can be recovered by using the 'files' function.
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The first 3 file entries always refer to standard input, output
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and error respectively. (see the example below) These three
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files are already open by the calculator and cannot be closed.
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When calc starts up, it scans for open file descriptors above
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stderr (2) and below MAXFILES (20). Any open descriptor found
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is assumed to be an open file opened in an unknown mode. Calc
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will try to read and write to this file when directed.
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Consider the following commands:
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$ echo "A line of text in the file on descriptor 5" > datafile
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$ calc 5<datafile
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then one could do the following:
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> files(5)
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FILE 5 "descriptor[5]" (unknown_mode, pos 0)
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> fgetline(files(5))
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"A line of text in the file on descriptor 5"
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EXAMPLE
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> fd = fopen("/etc/motd", "r")
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> fd
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FILE 3 "/etc/motd" (reading, pos 0)
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> files(3)
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FILE 3 "/etc/motd" (reading, pos 0)
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> if (isnull(files(4))) print "not open"
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not open
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> stdin = files(0)
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> stdout = files(1)
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> stderr = files(2)
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> print files()
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20
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LIMITS
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none
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LIBRARY
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none
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SEE ALSO
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errno, fclose, feof, ferror, fflush, fgetc, fgetline, fgets, files, fopen,
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fprintf, fputc, fputs, fseek, fsize, ftell, isfile, printf, prompt
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