initial commit

LICENSE

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+MIT License
+Copyright 2019 Bruce Hill <bruce@bruce-hill.com>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

Makefile

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+PREFIX=
+CC=cc
+CFLAGS=-O3 -std=gnu99
+
+all: arg
+
+clean:
+	rm arg
+
+arg: arg.c
+	$(CC) arg.c $(CFLAGS) -o arg
+	
+install: arg
+	@prefix="$(PREFIX)"; \
+	if [[ ! $$prefix ]]; then \
+		read -p $$'\033[1mWhere do you want to install? (default: /usr/local) \033[0m' prefix; \
+	fi; \
+	if [[ ! $$prefix ]]; then \
+		prefix="/usr/local"; \
+	fi; \
+	mkdir -pv $$prefix/bin $$prefix/share/man/man1 \
+	&& cp -v arg $$prefix/bin/ \
+	&& cp -v arg.1 $$prefix/share/man/man1/
+
+uninstall:
+	@prefix="$(PREFIX)"; \
+	if [[ ! $$prefix ]]; then \
+		read -p $$'\033[1mWhere do you want to uninstall from? (default: /usr/local) \033[0m' prefix; \
+	fi; \
+	if [[ ! $$prefix ]]; then \
+		prefix="/usr/local"; \
+	fi; \
+	echo "Deleting..."; \
+	rm -rvf $$prefix/bin/arg $$prefix/share/man/man1/arg.1
+

arg.c

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+/* 
+ * arg - A simple C program by Bruce Hill for parsing command line arguments
+ *   Licensed under the MIT license (see LICENSE for details).
+ *
+ *   Example: arg --foo a b --foo=blah --baz -xyz
+ *     - Prints "blah" and exits with success
+ *   Example: arg --nope a b --foo=blah --baz -xyz
+ *     - Prints nothing and exits with failure
+ *   Example: arg -y a b --foo=blah --baz -xyz
+ *     - Prints nothing and exits with success
+ */
+#include <stdio.h>
+#include <string.h>
+
+int main(int argc, char **argv)
+{
+    char *flag = argv[1];
+    if (!flag || flag[0] != '-') {
+        fprintf(stderr, "Usage: arg [-<f> | --<flag>] ...\n");
+        return 1;
+    }
+    size_t n = strlen(flag);
+    // Look for: --flag=val, --flag val, --flag, -f=val, -f val, or -f
+    for (int i = 2; i < argc; i++) {
+        char *arg = argv[i];
+        if (strncmp(arg, flag, n) != 0) continue;
+        if (arg[n] == '\0') { // --flag
+            if (argv[i+1] && argv[i+1][0] != '-')
+                puts(argv[i+1]); // value of flag, if any
+            return 0;
+        } else if (arg[n] == '=') { // --flag=...
+            puts(&arg[n+1]);
+            return 0;
+        }
+    }
+    // If flag is single-character, e.g. -f, look for it among other single
+    // character flags like -xfy, in which case the next argument will not
+    // be considered its value.
+    if (n == 2) {
+        for (int i = 2; i < argc; i++) {
+            char *arg = argv[i];
+            if (arg[0] != '-' || arg[1] == '-')
+                continue; // skip foo and --foo
+            for (char *c = &arg[1]; *c; c++) {
+                if (*c == flag[1]) return 0;
+            }
+        }
+    }
+    return 1;
+}