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Userland: Improve head program

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* allow specifying files as arguments, e.g. `head a b c`
* support multiple files
* print a filename header when multiple files are being printed
* allow suppression or forcing of filename header via flags

This change drops support for the legacy `-123` syntax in favour of the
more widely-supported `-n 123` form.

fixes #105
This commit is contained in:
Conrad Pankoff 2019-06-01 21:39:49 +10:00 committed by Andreas Kling
parent b8e705da0e
commit 6cabd34b93
Notes: sideshowbarker 2024-07-19 13:48:36 +09:00 
Author: https://github.com/deoxxa
Commit: https://github.com/SerenityOS/serenity/commit/6cabd34b939
Pull-request: https://github.com/SerenityOS/serenity/pull/155
Reviewed-by: https://github.com/awesomekling
1 changed files with 76 additions and 8 deletions
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84
Userland/head.cpp
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@ -1,26 +1,94 @@
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <LibCore/CArgsParser.h>
int head(const String& filename, bool print_filename, int line_count);
int main(int argc, char** argv)
{
// FIXME: Allow setting via command-line argument.
int line_count = 10;
CArgsParser args_parser("head");
if (argc > 1) {
for (int i = 1; i < argc; ++i) {
if (argv[i][0] == '-') {
line_count = atoi(&argv[i][1]);
}
args_parser.add_arg("n", "lines", "Number of lines to print (default 10)");
args_parser.add_arg("q", "Never print filenames");
args_parser.add_arg("v", "Always print filenames");
CArgsParserResult args = args_parser.parse(argc, (const char**)argv);
int line_count = 10;
if (args.is_present("n")) {
line_count = strtol(args.get("n").characters(), NULL, 10);
if (errno) {
args_parser.print_usage();
return -1;
}
}
Vector<String> files = args.get_single_values();
bool print_filenames = files.size() > 1;
if (args.is_present("v")) {
print_filenames = true;
} else if (args.is_present("q")) {
print_filenames = false;
}
if (files.is_empty()) {
return head("", print_filenames, line_count);
}
int rc = 0;
for (auto &file : files) {
if (head(file, print_filenames, line_count) != 0) {
rc = 1;
}
}
return rc;
}
int head(const String& filename, bool print_filename, int line_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());
}
}
for (int line = 0; line < line_count; ++line) {
char buffer[BUFSIZ];
auto* str = fgets(buffer, sizeof(buffer), stdin);
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);
}
fclose(fp);
if (print_filename) {
puts("");
}
return 0;
}