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Userland: Improve cat(1)

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* Port it to Core::ArgsParser - even though it doesn't support any options
  at the moment, it's nice to handle --help and reject other options;
* Accept "-" to mean stdin;
* Make sure to write out all data that we read, looping if needed;
* Detect Useless Uses of Cat and print a cute warning :^)
This commit is contained in:
Sergey Bugaev 2020-06-16 22:10:24 +03:00 committed by Andreas Kling
parent 6fcce077bb
commit c39045b222
Notes: sideshowbarker 2024-07-19 05:36:18 +09:00 
Author: https://github.com/bugaevc
Commit: https://github.com/SerenityOS/serenity/commit/c39045b222f
Pull-request: https://github.com/SerenityOS/serenity/pull/2564
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/awesomekling
1 changed files with 41 additions and 9 deletions
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50
Userland/cat.cpp
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@ -25,14 +25,31 @@
*/
#include <AK/Vector.h>
#include <LibCore/ArgsParser.h>
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <string.h>
#include <unistd.h>
bool detect_useless_use_of_cat(int argc)
{
// I can think of somewhat valid uses of zero-argument cat
// from a tty to a pipe, so let's allow those.
if (argc != 2)
return false;
struct stat statbuf;
int rc = fstat(1, &statbuf);
if (rc < 0)
return false;
return S_ISFIFO(statbuf.st_mode);
}
int main(int argc, char** argv)
{
if (pledge("stdio rpath", nullptr) < 0) {
@ -40,12 +57,23 @@ int main(int argc, char** argv)
return 1;
}
Vector<const char*> paths;
Core::ArgsParser args_parser;
args_parser.add_positional_argument(paths, "File path", "path", Core::ArgsParser::Required::No);
args_parser.parse(argc, argv);
if (detect_useless_use_of_cat(argc))
fprintf(stderr, "\033[34;1mMeow! Useless use of cat detected\033[0m\n");
Vector<int> fds;
if (argc > 1) {
for (int i = 1; i < argc; i++) {
if (!paths.is_empty()) {
for (const char* path : paths) {
int fd;
if ((fd = open(argv[i], O_RDONLY)) == -1) {
fprintf(stderr, "Failed to open %s: %s\n", argv[i], strerror(errno));
if (StringView { path } == "-") {
fd = 0;
} else if ((fd = open(path, O_RDONLY)) == -1) {
fprintf(stderr, "Failed to open %s: %s\n", path, strerror(errno));
continue;
}
fds.append(fd);
@ -69,14 +97,18 @@ int main(int argc, char** argv)
perror("read");
return 2;
}
ssize_t nwritten = write(1, buf, nread);
if (nwritten < 0) {
perror("write");
return 3;
size_t already_written = 0;
while (already_written < (size_t)nread) {
ssize_t nwritten = write(1, buf + already_written, nread - already_written);
if (nwritten < 0) {
perror("write");
return 3;
}
already_written += nwritten;
}
ASSERT(nwritten == nread);
}
close(fd);
}
return 0;
}