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/*
* 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 <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
int head(const String& filename, bool print_filename, ssize_t line_count, ssize_t byte_count);
int main(int argc, char** argv)
{
if (pledge("stdio rpath", nullptr) < 0) {
perror("pledge");
return 1;
}
int line_count = -1;
int byte_count = -1;
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(byte_count, "Number of bytes to print", "bytes", '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 == -1 && byte_count == -1) {
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, byte_count);
}
int rc = 0;
for (auto& file : files) {
if (head(file, print_filenames, line_count, byte_count) != 0) {
rc = 1;
}
}
return rc;
}
int head(const String& filename, bool print_filename, ssize_t line_count, ssize_t byte_count)
{
bool is_stdin = false;
int fd = -1;
ScopeGuard fd_close_guard = [&fd] {
if (fd > 0)
close(fd);
};
if (filename == "" || filename == "-") {
fd = 0;
is_stdin = true;
} else {
fd = open(filename.characters(), O_RDONLY);
if (fd < 0) {
warnln("Failed to open {}: {}", filename, strerror(errno));
return 1;
}
}
if (print_filename) {
if (is_stdin) {
outln("==> standard input <==");
} else {
outln("==> {} <==", filename);
}
}
fflush(stdout);
size_t buffer_size = line_count != -1 ? BUFSIZ : min((size_t)BUFSIZ, (size_t)byte_count);
char buffer[buffer_size];
while (line_count > 0 || byte_count > 0) {
size_t ntoread = line_count != -1 ? buffer_size : min(buffer_size, (size_t)byte_count);
ssize_t nread = read(fd, buffer, ntoread);
if (nread < 0) {
perror("read");
return 1;
} else if (nread == 0) {
break;
}
size_t ntowrite;
if (byte_count != -1) {
// Write out everything we've read, since we have explicitly ensured
// that we wouldn't read more than we want to write.
ntowrite = nread;
byte_count -= nread;
} else {
// Count line breaks.
ntowrite = 0;
while (line_count) {
const char* newline = strchr(buffer + ntowrite, '\n');
if (newline) {
// Found another line break, include this line.
ntowrite = newline - buffer + 1;
line_count--;
} else {
// No more line breaks, write the whole thing.
ntowrite = nread;
break;
}
}
}
size_t ncomplete = 0;
while (ncomplete < ntowrite) {
ssize_t nwritten = write(1, buffer + ncomplete, ntowrite - ncomplete);
if (nwritten < 0) {
perror("write");
return 1;
}
ncomplete += nwritten;
}
}
if (print_filename) {
puts("");
}
return 0;
}
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