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rev.c
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C/C++ Source or Header
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1990-07-19
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1KB
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70 lines
/* rev - reverse an ASCII line Authors: Paul Polderman & Michiel Huisjes */
#include <sys/types.h>
#include <fcntl.h>
#include <blocksize.h>
#ifndef EOF
#define EOF ((char) -1)
#endif
int fd; /* File descriptor from file being read */
main(argc, argv)
int argc;
char *argv[];
{
register unsigned short i;
if (argc == 1) { /* If no arguments given, use stdin as input */
fd = 0;
rev();
exit(0);
}
for (i = 1; i < argc; i++) { /* Reverse each line in arguments */
if ((fd = open(argv[i], O_RDONLY)) < 0) {
std_err("Cannot open ");
std_err(argv[i]);
std_err("\n");
continue;
}
rev();
close(fd);
}
exit(0);
}
rev()
{
char output[BLOCK_SIZE]; /* Contains a reversed line */
register unsigned short i; /* Index in output array */
do {
i = BLOCK_SIZE - 1;
while ((output[i] = nextchar()) != '\n' && output[i] != EOF) i--;
write(1, &output[i + 1], BLOCK_SIZE - 1 - i); /* write reversed line */
if (output[i] == '\n') /* and write a '\n' */
write(1, "\n", 1);
} while (output[i] != EOF);
}
char buf[BLOCK_SIZE];
nextchar()
{ /* Does a sort of buffered I/O */
static int n = 0; /* Read count */
static int i; /* Index in input buffer to next character */
if (--n <= 0) { /* We've had this block. Read in next block */
n = read(fd, buf, BLOCK_SIZE);
i = 0; /* Reset index in array */
}
return((n <= 0) ? EOF : buf[i++]); /* Return -1 on EOF */
}