47 lines
852 B
C
47 lines
852 B
C
/* lineup.c
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Converts a file to uppercase in-place.
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Incidentally, another way to do this while avoiding the seeks
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would be to open the input file, then remove() it and reopen
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it under another handle. Because of Unix deletion semantics
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this works fine. */
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#include <ctype.h>
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#include <stdio.h>
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#include <syscall.h>
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int
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main (int argc, char *argv[])
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{
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char buf[1024];
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int handle;
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if (argc != 2)
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exit (1);
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handle = open (argv[1]);
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if (handle < 0)
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exit (2);
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for (;;)
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{
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int n, i;
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n = read (handle, buf, sizeof buf);
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if (n <= 0)
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break;
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for (i = 0; i < n; i++)
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buf[i] = toupper ((unsigned char) buf[i]);
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seek (handle, tell (handle) - n);
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if (write (handle, buf, n) != n)
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printf ("write failed\n");
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}
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close (handle);
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return EXIT_SUCCESS;
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}
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