70 lines
1.4 KiB
C
70 lines
1.4 KiB
C
/* rev - reverse an ASCII line Authors: Paul Polderman & Michiel Huisjes */
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#include <sys/types.h>
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#include <fcntl.h>
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#include <blocksize.h>
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#ifndef EOF
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#define EOF ((char) -1)
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#endif
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int fd; /* File descriptor from file being read */
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main(argc, argv)
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int argc;
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char *argv[];
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{
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register unsigned short i;
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if (argc == 1) { /* If no arguments given, use stdin as input */
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fd = 0;
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rev();
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exit(0);
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}
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for (i = 1; i < argc; i++) { /* Reverse each line in arguments */
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if ((fd = open(argv[i], O_RDONLY)) < 0) {
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std_err("Cannot open ");
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std_err(argv[i]);
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std_err("\n");
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continue;
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}
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rev();
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close(fd);
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}
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exit(0);
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}
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rev()
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{
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char output[BLOCK_SIZE]; /* Contains a reversed line */
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register unsigned short i; /* Index in output array */
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do {
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i = BLOCK_SIZE - 1;
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while ((output[i] = nextchar()) != '\n' && output[i] != EOF) i--;
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write(1, &output[i + 1], BLOCK_SIZE - 1 - i); /* write reversed line */
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if (output[i] == '\n') /* and write a '\n' */
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write(1, "\n", 1);
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} while (output[i] != EOF);
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}
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char buf[BLOCK_SIZE];
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nextchar()
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{ /* Does a sort of buffered I/O */
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static int n = 0; /* Read count */
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static int i; /* Index in input buffer to next character */
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if (--n <= 0) { /* We've had this block. Read in next block */
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n = read(fd, buf, BLOCK_SIZE);
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i = 0; /* Reset index in array */
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}
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return((n <= 0) ? EOF : buf[i++]); /* Return -1 on EOF */
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}
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