refactor and xargs

1 files changed, 163 insertions, 0 deletions

diff --git a/src/commands/xargs.c b/src/commands/xargs.c
new file mode 100644
index 0000000..3b96bb6
--- /dev/null
+++ b/src/commands/xargs.c
@@ -0,0 +1,163 @@
+#include "../command.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+static struct {
+    bool null_seperated;
+    bool ignore_empty;
+    bool print_command;
+    bool prompt_command;
+    int max_args;
+    FILE* file;
+} flags;
+
+static void help(void) {
+    printf("Usage: xargs [OPTIONS] [PROG ARGS]\n\n");
+    printf("Run PROG on every item given by stdin\n\n");
+	printf("\t-0\tInput is separated by NULs\n");
+	printf("\t-a FILE\tRead from FILE instead of stdin\n");
+	printf("\t-r\tDon't run command if input is empty\n");
+	printf("\t-t\tPrint the command on stderr before execution\n");
+	printf("\t-p\tAsk user whether to run each command\n");
+	printf("\t-n N\tPass no more than N args to PROG\n");
+}
+
+static int short_arg(char c, char* next) {
+    UNUSED(next);
+    switch (c) {
+        case '0':
+            flags.null_seperated = true;
+            break;
+        case 'a':
+            check_arg(next);
+            flags.file = get_file(next, "r");
+            return ARG_USED;
+        case 'r':
+            flags.ignore_empty = true;
+            break;
+        case 't':
+            flags.print_command = true;
+            break;
+        case 'p':
+            flags.prompt_command = true;
+            break;
+        case 'n':
+            check_arg(next);
+            long int n = get_number(next);
+            if (n < 1) {
+                error("error: max arg count must be at least 1");
+            }
+            return ARG_USED;
+    }
+    return ARG_UNUSED;
+}
+
+char* read_next(FILE* file, int arg_count) {
+
+    if (arg_count == flags.max_args) return NULL;
+
+    int size = 0;
+    int capacity = 8;
+    char* buf = malloc(sizeof(char) * capacity);
+
+    char c;
+    while(c = getc(file), true) {
+        if (c == EOF && size == 0) {
+            free(buf);
+            return NULL;
+        }
+
+        if (size == capacity) {
+            capacity *= 2;
+            buf = realloc(buf, sizeof(char) * capacity);
+        }
+
+        if (c == '\0' || c == EOF || (!flags.null_seperated && c == '\n')) {
+            buf[size++] = '\0';
+            return buf;
+        } else {
+            buf[size++] = c;
+        }
+    }
+}
+
+void read_args(FILE* file, char*** args, int* size, int* capacity) {
+    char* arg;
+    while (arg = read_next(file, *size), true) {
+        if (*size == *capacity) {
+            *capacity *= 2;
+            *args = realloc(*args, sizeof(char*) * *capacity);
+        }
+        (*args)[(*size)++] = arg;
+        if (arg == NULL) break;
+    }
+}
+
+COMMAND(xargs) {
+    flags.null_seperated = false;
+    flags.ignore_empty = false;
+    flags.print_command = false;
+    flags.print_command = false;
+    flags.max_args = -1;
+    flags.file = stdin;
+
+    int start = parse_args(argc, argv, help, short_arg, NULL);
+
+    char* command;
+    if (start >= argc) {
+        command = "echo";
+    } else {
+        command = argv[start]; 
+    }
+
+    int arg_start = start + 1;
+    int arg_on_stack_count;
+
+    if (arg_start >= argc) {
+        arg_on_stack_count = 0;
+        arg_start = argc - 1;
+    } else {
+        arg_on_stack_count = argc - arg_start;
+    }
+
+    int size = arg_on_stack_count + 1;
+    int capacity = size + 8;
+    char** args = malloc(sizeof(char*) * capacity);
+    args[0] = command;
+    memcpy(&args[1], &argv[arg_start], arg_on_stack_count * sizeof(char*));
+    read_args(flags.file, &args, &size, &capacity);
+
+    if (flags.ignore_empty && size < 2) goto cleanup;
+
+    if (flags.prompt_command || flags.print_command) {
+        for (int i = 0; i < size - 1; i++) {
+            fprintf(stderr, "%s ", args[i]);
+        }
+        fprintf(stderr, "\b\n");
+    }
+
+    if (flags.prompt_command) {
+        fprintf(stderr, "Run command? ");
+        fflush(stderr);
+        FILE* in = get_tty_stream("r");
+        char c = getc(in);
+        fclose(in);
+        if (c != 'y' && c != 'Y') {
+            fprintf(stderr, "Skipping...\n");
+            goto cleanup;
+        }
+    }
+
+    if (execvp(command, args) == -1) {
+        error("error: failed to execute command: %s", strerror(errno));
+    }
+
+cleanup:
+
+    for (int i = arg_on_stack_count + 1; i < size - 1; i++) {
+        free(args[i]);
+    }
+    fclose(flags.file);
+
+    return EXIT_SUCCESS;
+}