added tail and head

1 files changed, 175 insertions, 31 deletions

diff --git a/src/commands/tail.c b/src/commands/tail.c
index 04f7f42..24d7b1f 100644
--- a/src/commands/tail.c
+++ b/src/commands/tail.c
@@ -2,19 +2,31 @@
 
 #include <stdio.h>
 #include <string.h>
+#include <sys/select.h>
 #include <sys/stat.h>
+#include <unistd.h>
 
-static void tail_file(FILE* file) {
-    char* ring[10];
-    memset(ring, 0, sizeof(char*) * 10);
+struct Flags {
+    bool lines;
+    int count;
+    bool print_headers;
+    bool dont_print_headers;
+    bool print_as_grow;
+    int grow_wait;
+};
 
-    int ring_len[10];
+static size_t tail_file_lines(FILE* file, unsigned int count, size_t skip) {
+    char* ring[count];
+    memset(ring, 0, sizeof(char*) * count);
+
+    int ring_len[count];
     
     int index = 0;
-    int size = 0;
+    unsigned int size = 0;
 
     int read;
-    size_t len = 0;
+    fseek(file, skip, SEEK_SET);
+    size_t len = skip;
     char* line = NULL;
     while ((read = getline(&line, &len, file)) != -1) {
 
@@ -23,57 +35,189 @@ static void tail_file(FILE* file) {
         ring_len[index] = read;
 
         index++;
-        index %= 10;
-        if (size < 10) size++;
+        index %= count;
+        if (size < count) size++;
 
         line = NULL;
     }
 
-    index += 10 - size;
-    index %= 10;
+    index += count - size;
+    index %= count;
     
-    for (int i = 0; i < size; i++) {
+    for (unsigned int i = 0; i < size; i++) {
         fwrite(ring[index], ring_len[index], 1, stdout);
         free(ring[index]);
         index += 1;
-        index %= 10;
+        index %= count;
     }
 
     free(line);
     fclose(file);
+
+    return len;
+}
+
+static size_t tail_file_chars(FILE* file, unsigned int count, size_t skip) {
+    char ring[count];
+    memset(ring, 0, count);
+
+    int index = 0;
+    unsigned int size = 0;
+
+    fseek(file, skip, SEEK_SET);
+    int read = skip;
+    int c;
+    while((c = getc(file)) != EOF) {
+        ring[index] = c;
+        index++;
+        read++;
+        index %= count;
+        if (size < count) size++;
+    }
+
+    index += count - size;
+    index %= count;
+
+    for (unsigned int i = 0; i < size; i++) {
+        putchar(ring[index]);
+        index += 1;
+        index %= count;
+    }
+
+    fclose(file);
+
+    return read;
 }
 
 static void help() {
-    printf("Usage: tail [FILE]...\n\n");
+    printf("Usage: tail [OPTIONS] [FILE]...\n\n");
     printf("Print last 10 lines of FILEs (or stdin) to.\n");
-    printf("With more than one FILE, precede each with a filename header.\n");
+    printf("With more than one FILE, precede each with a filename header.\n\n");
+    printf("\t-c [+]N[bkm]\tPrint last N bytes\n");
+	printf("\t-n N[bkm]\tPrint last N lines\n");
+	printf("\t\t\t(b:*512 k:*1024 m:*1024^2)\n");
+	printf("\t-q\t\tNever print headers\n");
+	printf("\t-v\t\tAlways print headers\n");
+	printf("\t-f\t\tPrint data as file grows\n");
+	printf("\t-s SECONDS\tWait SECONDS between reads with -f\n");
     exit(EXIT_SUCCESS);
 }
 
+static char* next_arg(int argc, char** argv, int index) {
+    if (index >= argc) {
+        error("error: expected another argument after option");
+    }
+    return argv[index];
+}
+
+static void print_header(char* path, struct Flags* flags, bool many) {
+    if (flags->dont_print_headers) return;
+    if (!many && !flags->print_headers) return;
+    if (streql("-", path)) {
+        printf("\n==> standard input <==\n");
+    } else {
+        printf("\n=>> %s <==\n", path);
+    }
+}
+
+static void tail_file(char* path, struct Flags* flags, bool many) {
+    FILE* file = get_file(path, "r");
+    print_header(path, flags, many);
+    
+    size_t skip = 0;
+    while (true) {
+        if (flags->lines) {
+            skip = tail_file_lines(file, flags->count, skip);
+        } else {
+            skip = tail_file_chars(file, flags->count, skip);
+        }
+        if (!flags->print_as_grow) break;
+        sleep(flags->grow_wait);
+        get_file(path, "r");
+    };
+}
+
 COMMAND(tail) {
-    if (argc < 1) {
-        tail_file(stdin);
-        return EXIT_SUCCESS;
+
+    struct Flags flags;
+    flags.count = 10;
+    flags.dont_print_headers = false;
+    flags.print_headers = false;
+    flags.lines = true;
+    flags.print_as_grow = false;
+    flags.grow_wait = 10;
+
+    int start = 0;
+    for (int i = 0; i < argc; i++) { 
+        if (!prefix("-", argv[i])) break;
+        if (streql(argv[0], "--help")) help();
+        start++;
+        int i_s = i;
+        for (size_t j = 1; j < strlen(argv[i_s]); j++) {
+            char c = argv[i_s][j];
+            switch(c) {
+                case 'c': {
+                    start++;
+                    flags.lines = false;
+                    char* arg = next_arg(argc, argv, ++i);
+                    long int bkm = get_blkm(arg);
+                    if (bkm < 1) {
+                        error("error: bkm cannot be less than 1");
+                    }
+                    flags.count = bkm;
+                    break;
+                }
+                case 'n': {
+                    start++;
+                    flags.lines = true;
+                    char* arg = next_arg(argc, argv, ++i);
+                    long int bkm = get_blkm(arg);
+                    if (bkm < 1) {
+                        error("error: bkm cannot be less than 1");
+                    }
+                    flags.count = bkm;
+                    break;
+                }
+                case 'q':
+                    flags.dont_print_headers = true;
+                    break;
+                case 'v':
+                    flags.print_headers = true;
+                    break;
+                case 'f':
+                    flags.print_as_grow = true;
+                    break;
+                case 's': {
+                    start++;
+                    char* arg = next_arg(argc, argv, ++i);
+                    long int sec = get_number(arg);
+                    if (sec < 1) {
+                        error("error: wait seconds cannot be less than 1");
+                    }
+                    flags.grow_wait = sec;
+                    break;
+                }
+                default: {
+                    error("error: unknown option -%c", c);
+                }
+            }
+        }
     }
 
-    if (streql(argv[0], "--help")) help();
+    int count = argc - start;
 
-    if (argc == 1) {
-        FILE* file = get_file(argv[0], "r");
-        tail_file(file);
+    if (count < 1) {
+        tail_file_lines(stdin, 10, 0);
         return EXIT_SUCCESS;
     }
 
-    for (int i = 0; i < argc; i++) {
-        FILE* file;
-        if (streql("-", argv[i])) {
-            file = stdin;
-        } else {
-            file = get_file_s(argv[i], "r");
-            if (file == NULL) continue;
-        }
-        printf("\n==> %s <==\n", argv[i]);
-        tail_file(file);
+    if (count == 1) {
+        tail_file(argv[start], &flags, false);
+        return EXIT_SUCCESS;
+    }
+
+    for (int i = 0; i < count; i++) {
+        tail_file(argv[start + i], &flags, true);
     }
 
     return EXIT_SUCCESS;