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
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
|
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/StdLibExtras.h>
#include <LibCore/ArgsParser.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
int head(const String& filename, bool print_filename, int line_count, int char_count);
int main(int argc, char** argv)
{
if (pledge("stdio rpath", nullptr) < 0) {
perror("pledge");
return 1;
}
int line_count = 0;
int char_count = 0;
bool never_print_filenames = false;
bool always_print_filenames = false;
Vector<const char*> files;
Core::ArgsParser args_parser;
args_parser.set_general_help("Print the beginning ('head') of a file.");
args_parser.add_option(line_count, "Number of lines to print (default 10)", "lines", 'n', "number");
args_parser.add_option(char_count, "Number of characters to print", "characters", 'c', "number");
args_parser.add_option(never_print_filenames, "Never print filenames", "quiet", 'q');
args_parser.add_option(always_print_filenames, "Always print filenames", "verbose", 'v');
args_parser.add_positional_argument(files, "File to process", "file", Core::ArgsParser::Required::No);
args_parser.parse(argc, argv);
if (line_count == 0 && char_count == 0) {
line_count = 10;
}
bool print_filenames = files.size() > 1;
if (always_print_filenames)
print_filenames = true;
else if (never_print_filenames)
print_filenames = false;
if (files.is_empty()) {
return head("", print_filenames, line_count, char_count);
}
int rc = 0;
for (auto& file : files) {
if (head(file, print_filenames, line_count, char_count) != 0) {
rc = 1;
}
}
return rc;
}
int head(const String& filename, bool print_filename, int line_count, int char_count)
{
bool is_stdin = false;
FILE* fp = nullptr;
if (filename == "" || filename == "-") {
fp = stdin;
is_stdin = true;
} else {
fp = fopen(filename.characters(), "r");
if (!fp) {
fprintf(stderr, "can't open %s for reading: %s\n", filename.characters(), strerror(errno));
return 1;
}
}
if (print_filename) {
if (is_stdin) {
puts("==> standard input <==");
} else {
printf("==> %s <==\n", filename.characters());
}
}
if (line_count) {
for (int line = 0; line < line_count; ++line) {
char buffer[BUFSIZ];
auto* str = fgets(buffer, sizeof(buffer), fp);
if (!str)
break;
// specifically use fputs rather than puts, because fputs doesn't add
// its own newline.
fputs(str, stdout);
}
} else if (char_count) {
char buffer[BUFSIZ];
while (char_count) {
int nread = fread(buffer, 1, min(BUFSIZ, char_count), fp);
if (nread > 0) {
int ncomplete = 0;
while (ncomplete < nread) {
int nwrote = fwrite(&buffer[ncomplete], 1, nread - ncomplete, stdout);
if (nwrote > 0)
ncomplete += nwrote;
if (feof(stdout)) {
fprintf(stderr, "unexpected eof writing to stdout\n");
return 1;
}
if (ferror(stdout)) {
fprintf(stderr, "error writing to stdout\n");
return 1;
}
}
}
char_count -= nread;
if (feof(fp))
break;
if (ferror(fp)) {
fprintf(stderr, "error reading input\n");
break;
}
}
}
fclose(fp);
if (print_filename) {
puts("");
}
return 0;
}
|
