Userland: Move command-line utilities to Userland/Utilities/

Userland/Utilities/head.cpp

@@ -0,0 +1,162 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <AK/StdLibExtras.h>
+#include <LibCore/ArgsParser.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.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 file names", "quiet", 'q');
+    args_parser.add_option(always_print_filenames, "Always print file names", "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;
+}