1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
|
#include "../command.h"
static struct {
int count;
bool lines;
bool print_headers;
bool dont_print_headers;
} flags;
static void head_file_lines(FILE* file) {
size_t len = 0;
char* line = NULL;
int count = flags.count;
while(count > 0 && getline(&line, &len, file) != -1) {
printf("%s", line);
count--;
}
free(line);
fclose(file);
}
static void head_file_chars(FILE* file) {
char c;
int count = flags.count;
while(count > 0 && (c = getc(file)) != EOF) {
putchar(c);
count--;
}
fclose(file);
}
static void help(void) {
printf("Usage: head [OPTIONS] [FILE]...\n\n");
printf("Print first 10 lines of FILEs (or stdin)\n");
printf("With more than one FILE, precede each with a filename header.\n\n");
printf("\t-c [+]N[bkm]\tPrint first N bytes\n");
printf("\t-n N[bkm]\tPrint first N lines\n");
printf("\t\t\t(b:*512 k:*1024 m:*1024^2)\n");
printf("\t-q\t\tNever print headers\n");
printf("\t-v\t\tAlways print headers\n");
}
static void print_header(char* path, bool many) {
if (flags.dont_print_headers) return;
if (!many && !flags.print_headers) return;
if (streql("-", path)) {
printf("\n==> standard input <==\n");
} else {
printf("\n=>> %s <==\n", path);
}
}
static void head_file(char* path, bool many) {
FILE* file = get_file(path, "r");
print_header(path, many);
if (flags.lines) {
head_file_lines(file);
} else {
head_file_chars(file);
}
}
static int short_arg(char c, char* next) {
switch(c) {
case 'c': {
flags.lines = false;
check_arg(next);
long int bkm = get_blkm(next);
if (bkm < 1) {
error("error: bkm cannot be less than 1");
}
flags.count = bkm;
return ARG_USED;
}
case 'n': {
flags.lines = true;
check_arg(next);
long int bkm = get_blkm(next);
if (bkm < 1) {
error("error: bkm cannot be less than 1");
}
flags.count = bkm;
return ARG_USED;
}
case 'q':
flags.dont_print_headers = true;
break;
case 'v':
flags.print_headers = true;
break;
default: {
error("error: unknown option -%c", c);
}
}
return ARG_UNUSED;
}
COMMAND(head) {
flags.count = 10;
flags.lines = true;
flags.print_headers = false;
flags.dont_print_headers = false;
int start = parse_args(argc, argv, help, short_arg, NULL);
int count = argc - start;
if (count < 1) {
head_file_lines(stdin);
return EXIT_SUCCESS;
}
if (count == 1) {
head_file(argv[start], false);
return EXIT_SUCCESS;
}
for (int i = 0; i < count; i++) {
head_file(argv[start + i], true);
}
return EXIT_SUCCESS;
}
|
