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Userland: Implement -c [characters] option for head

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This commit is contained in:
Conrad Pankoff 2019-06-08 23:30:42 +10:00 • committed by Andreas Kling
parent 842bf96e2c
commit 7b04c7dc48
1 changed files with 76 additions and 13 deletions
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89
Userland/head.cpp
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@ -1,27 +1,53 @@
#include <AK/StdLibExtras.h>
#include <LibCore/CArgsParser.h> #include <LibCore/CArgsParser.h>
#include <errno.h> #include <errno.h>
#include <stdio.h> #include <stdio.h>
#include <stdlib.h> #include <stdlib.h>
int head(const String& filename, bool print_filename, int line_count); int head(const String& filename, bool print_filename, int line_count, int char_count);
int main(int argc, char** argv) int main(int argc, char** argv)
{ {
CArgsParser args_parser("head"); CArgsParser args_parser("head");
args_parser.add_arg("n", "lines", "Number of lines to print (default 10)"); args_parser.add_arg("n", "lines", "Number of lines to print (default 10)");
args_parser.add_arg("c", "characters", "Number of characters to print");
args_parser.add_arg("q", "Never print filenames"); args_parser.add_arg("q", "Never print filenames");
args_parser.add_arg("v", "Always print filenames"); args_parser.add_arg("v", "Always print filenames");
CArgsParserResult args = args_parser.parse(argc, (const char**)argv); CArgsParserResult args = args_parser.parse(argc, (const char**)argv);
int line_count = 10; int line_count = 0;
if (args.is_present("n")) { if (args.is_present("n")) {
line_count = strtol(args.get("n").characters(), NULL, 10); line_count = strtol(args.get("n").characters(), NULL, 10);
if (errno) { if (errno) {
args_parser.print_usage(); args_parser.print_usage();
return -1; return -1;
} }
if (!line_count) {
args_parser.print_usage();
return -1;
}
}
int char_count = 0;
if (args.is_present("c")) {
char_count = strtol(args.get("c").characters(), NULL, 10);
if (errno) {
args_parser.print_usage();
return -1;
}
if (!char_count) {
args_parser.print_usage();
return -1;
}
}
if (line_count == 0 && char_count == 0) {
line_count = 10;
} }
Vector<String> files = args.get_single_values(); Vector<String> files = args.get_single_values();
@ -35,13 +61,13 @@ int main(int argc, char** argv)
} }
if (files.is_empty()) { if (files.is_empty()) {
return head("", print_filenames, line_count); return head("", print_filenames, line_count, char_count);
} }
int rc = 0; int rc = 0;
for (auto& file : files) { for (auto& file : files) {
if (head(file, print_filenames, line_count) != 0) { if (head(file, print_filenames, line_count, char_count) != 0) {
rc = 1; rc = 1;
} }
} }
@ -49,7 +75,7 @@ int main(int argc, char** argv)
return rc; return rc;
} }
int head(const String& filename, bool print_filename, int line_count) int head(const String& filename, bool print_filename, int line_count, int char_count)
{ {
bool is_stdin = false; bool is_stdin = false;
FILE* fp = nullptr; FILE* fp = nullptr;
@ -73,15 +99,52 @@ int head(const String& filename, bool print_filename, int line_count)
} }
} }
for (int line = 0; line < line_count; ++line) { if (line_count) {
char buffer[BUFSIZ]; for (int line = 0; line < line_count; ++line) {
auto* str = fgets(buffer, sizeof(buffer), fp); char buffer[BUFSIZ];
if (!str) auto* str = fgets(buffer, sizeof(buffer), fp);
break; if (!str)
break;
// specifically use fputs rather than puts, because fputs doesn't add // specifically use fputs rather than puts, because fputs doesn't add
// its own newline. // its own newline.
fputs(str, stdout); 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); fclose(fp);