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#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <errno.h>
#include <stdarg.h>
typedef enum
{
VLEVEL_QUIET,
VLEVEL_NORMAL,
VLEVEL_VERBOSE,
} t_verbose_level;
typedef enum
{
UNIT_LINE,
UNIT_BYTE,
} t_unit;
char *g_name = "head";
#define UNIT_BYTE_BUFFER_SIZE 1028
void fatal_printf(const char *format, ...)
{
va_list ap;
va_start(ap, format);
fprintf(stderr, "%s: ", g_name);
vfprintf(stderr, format, ap);
va_end(ap);
exit(EXIT_FAILURE);
}
int file_head(FILE *file,
char *header, t_unit unit,
unsigned long count, char line_delimiter)
{
char buf[UNIT_BYTE_BUFFER_SIZE] = {'\0'};
size_t read_size;
size_t write_size;
char *line = NULL;
size_t line_size = 0;
ssize_t ret;
if (header != NULL)
printf("==> %s <==\n", header);
switch (unit)
{
case UNIT_BYTE:
while (count > 0)
{
read_size = count > UNIT_BYTE_BUFFER_SIZE ? UNIT_BYTE_BUFFER_SIZE : count;
write_size = fread(buf, 1, read_size, file);
fwrite(buf, 1, write_size, stdout);
if (write_size < read_size)
break;
count -= read_size;
}
break;
case UNIT_LINE:
for (; count > 0 && (ret = getdelim(&line, &line_size, line_delimiter, file)) != -1; count--)
fwrite(line, 1, ret, stdout);
free(line);
break;
}
return 0;
}
int file_path_head(char *path,
char *header, t_unit unit,
unsigned long count, char line_delimiter)
{
FILE *file;
if ((file = fopen(path, "r")) == NULL)
{
fprintf(stderr, "%s: cannot open '%s' for reading: %s\n", g_name, path, strerror(errno));
return -1;
}
file_head(file, header, unit, count, line_delimiter);
fclose(file);
return 0;
}
int main(int argc, char **argv)
{
int option;
t_verbose_level verbose_level = VLEVEL_NORMAL;
t_unit unit = UNIT_LINE;
unsigned long count = 10;
char line_delimiter = '\n';
g_name = argv[0];
while ((option = getopt(argc, argv, "c:n:qvz")) != -1)
{
switch (option)
{
case 'c':
case 'n':
if (strchr(optarg, '-') != NULL)
fatal_printf("invalid number of bytes: '%s'\n", optarg);
char *endptr;
errno = 0;
// TODO '-' prefix result in tail
// TODO human readable size suffix
count = strtoul(optarg, &endptr, 10);
if (*endptr != '\0')
fatal_printf("invalid number of bytes: '%s'\n", optarg);
if (errno != 0 || *endptr != '\0')
fatal_printf("invalid number of bytes: '%s': %s\n", optarg, strerror(errno));
switch (option)
{
case 'c': unit = UNIT_BYTE; break;
case 'n': unit = UNIT_LINE; break;
}
break;
case 'q': verbose_level = VLEVEL_QUIET; break;
case 'v': verbose_level = VLEVEL_VERBOSE; break;
case 'z': line_delimiter = '\0'; break;
}
}
if (argv[optind] == NULL)
{
file_head(
stdin, verbose_level == VLEVEL_VERBOSE ? "standard input" : NULL,
unit, count, line_delimiter);
return EXIT_SUCCESS;
}
if (argv[optind + 1] == NULL)
{
if (strcmp(argv[optind], "-") == 0)
file_head(
stdin, verbose_level == VLEVEL_VERBOSE ? "standard input" : NULL,
unit, count, line_delimiter);
else
file_path_head(
argv[optind], verbose_level == VLEVEL_VERBOSE ? argv[optind] : NULL,
unit, count, line_delimiter);
return EXIT_SUCCESS;
}
for (; optind < argc; optind++)
{
int ret = 0;
if (strcmp(argv[optind], "-") == 0)
ret = file_head(
stdin, verbose_level != VLEVEL_QUIET ? "standard input" : NULL,
unit, count, line_delimiter);
else
ret = file_path_head(
argv[optind], verbose_level != VLEVEL_QUIET ? argv[optind] : NULL,
unit, count, line_delimiter);
if (argv[optind + 1] != NULL && ret != -1)
putchar('\n');
}
return EXIT_SUCCESS;
}
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