Added a bunch of enums for the ELF header.

.gitignore

@@ -1,2 +1,3 @@
 *.o
 bin/*
+.vscode/*

build.sh

@@ -0,0 +1,2 @@
+gcc -o main.o main.c
+./main.o "$1"

futil.c

@@ -0,0 +1,64 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+#ifndef FUTIL_READ_SIZE
+#define FUTIL_READ_SIZE 2097152 //Default here is 2MiB
+#endif
+
+//Reference: https://stackoverflow.com/a/44894946
+int ReadAllString(const char* path, char** content_ptr, size_t* bytes_read) {
+    if (!path || !content_ptr || !bytes_read) return 0;
+
+    FILE *file = fopen(path, "rb");
+
+    if (!file) {
+        fprintf(stderr, "Failed to open '%s'. %s.\n", path, strerror(errno));
+        return 0;
+    }
+
+    char *content = NULL, *temp = NULL;
+    size_t used = 0, capacity = 0, read = 0;
+
+    while(1) {
+        if (used + FUTIL_READ_SIZE + 1 > capacity) {
+            capacity = used + FUTIL_READ_SIZE + 1;
+
+            temp = realloc(content, capacity);
+
+            if (!temp) {
+                fprintf(stderr, "Failed to realloc space for file contents. %s.\n", strerror(errno));
+                free(content);
+                fclose(file);
+                return 0;
+            }
+
+            content = temp;
+        }
+
+        read = fread(content + used, 1, FUTIL_READ_SIZE, file);
+
+        if (read == 0) break;
+
+        used += read;
+    }
+
+    fclose(file);
+    //Shrink the buffer to fit just the contents of the buffer.
+    temp = realloc(content, used + 1);
+
+    if (!temp) {
+        fprintf(stderr, "Failed to realloc to only hold the file contents. %s.\n", strerror(errno));
+        free(content);
+        return 0;
+    }
+
+    content = temp;
+    content[used] = '\0';
+
+    *content_ptr = content;
+    *bytes_read = used;
+
+    return 1;
+}

main.c

@@ -1,6 +1,227 @@
 #include <stdio.h>
+#include "futil.c"
+
+typedef enum EIdent
+{
+	EI_MAG0 = 0, //Magic number position zero - three.
+	EI_MAG1 = 1,
+	EI_MAG2 = 2,
+	EI_MAG3 = 3,
+	EI_CLASS = 4,
+	EI_DATA = 5,
+	EI_VERSION = 6,
+	EI_OSABI = 7,
+	EI_ABIVERSION = 8,
+	EI_PAD = 9,
+	EI_NIDENT = 16 //End of reserved 16 bytes for the header.
+} EIdent;
+
+typedef enum EIClass
+{
+	ELFClassNone = 0,
+	ELFClass32 = 1,
+	ELFClass64 = 2
+} EIClass;
+
+typedef enum EI_Data
+{
+	ELFDataNone = 0,
+	ELFDataLSB = 1,
+	ELFDataMSB = 2
+} EIData;
+
+typedef enum ELFType{
+	ET_None = 0,		//No file type
+	ET_Rel = 1,			//Relocatable file
+	ET_Exec = 2,		//Executable file
+	ET_Dyn = 3,			//Shared object file
+	ET_Core = 4,		//Core file
+	ET_LOProc = 0xff00, //Processor
+	ET_HIProc = 0xffff  //Specific
+} ELFType;
+
+typedef enum ELFMachine
+{
+	EM_None = 0,
+	EM_M32 = 1, //AT&T WE 32100
+	EM_Sparc = 2,
+	EM_386 = 3,
+	EM_68k = 4,
+	EM_88k = 5,
+	EM_860 = 7,
+	EM_MIPS = 8
+} ELFMachine;
+
+typedef enum ELFOSABI
+{
+	ELFOSABI_NONE = 0,
+	ELFOSABI_HPUX = 1,
+	ELFOSABI_NETBSD = 2,
+	ELFOSABI_GNU = 3,
+	ELFOSABI_LINUX = 3,
+	ELFOSABI_SOLARIS = 6,
+	ELFOSABI_AIX,
+	ELFOSABI_IRIX,
+	ELFOSABI_FREEBSD,
+	ELFOSABI_TRU64,
+	ELFOSABI_MODESTO,
+	ELFOSABI_OPENBSD,
+	ELFOSABI_OPENVMS,
+	ELFOSABI_NSK,
+	ELFOSABI_AROS,
+	ELFOSABI_FENIXOS,
+	ELFOSABI_CLOUDABI,
+	ELFOSABI_OPENVOS
+} ELFOSABI;
 
 int main(int argc, char** argv)
 {
-	printf("Hello, world!\n");
+	char* bytes;
+	size_t size;
+
+	if (argc != 2)
+	{
+		printf("No argcs\n");
+		return 0;
+	}
+
+	if (!ReadAllString(argv[1], &bytes, &size)) return 0;
+
+	char magic[5] = { bytes[EI_MAG0], bytes[EI_MAG1], bytes[EI_MAG2], bytes[EI_MAG3], '\0' };
+
+	if (strcmp(magic, "\x7f""ELF") != 0) 
+	{
+		fprintf(stderr, "Failed to find ELF magic number in file header.\n");
+
+		return 0;
+	}
+	else printf("Magic ELF number found!\n");
+
+	switch(bytes[EI_CLASS])
+	{
+		case ELFClass32:
+			printf("32-bit object detected\n");
+			break;
+		case ELFClass64:
+			printf("64-bit object detected\n");
+			break;
+		default:
+			printf("Invalid class type detected\n");
+			return 1;
+	}
+
+	switch(bytes[EI_DATA])
+	{
+		case ELFDataLSB:
+			printf("2's complement, little endian.\n");
+			break;
+		case ELFDataMSB:
+			printf("2's complement, big endian.\n");
+			break;
+		default:
+			printf("Unknown byte order\n");
+			return 1;
+	}
+
+	if (bytes[EI_VERSION] == 1) printf("Version: current\n");
+	else printf("Invalid version number\n");
+
+	switch(bytes[EI_OSABI])
+	{
+		case ELFOSABI_NONE:
+			printf("No extension or unspecified OS ABI.\n");
+			break;
+		case ELFOSABI_HPUX:
+			printf("Hewlett-Packard HP-UX ABI\n");
+			break;
+		case ELFOSABI_NETBSD:
+			printf("NetBSD ABI\n");
+			break;
+		case ELFOSABI_LINUX:
+			printf("GNU ABI\n");
+			break;
+		case ELFOSABI_SOLARIS:
+			printf("Sun Solaris ABI\n");
+			break;
+		case ELFOSABI_AIX:
+			printf("AIX ABI\n");
+			break;
+		case ELFOSABI_IRIX:
+			printf("IRIX ABI\n");
+			break;
+		case ELFOSABI_FREEBSD:
+			printf("FreeBSd ABI\n");
+			break;
+		case ELFOSABI_TRU64:
+			printf("Compaq TRU64 UNIX ABI\n");
+			break;
+		case ELFOSABI_MODESTO:
+			printf("Novell Modesto ABI\n");
+			break;
+		case ELFOSABI_OPENBSD:
+			printf("OpenBSD ABI\n");
+			break;
+		case ELFOSABI_OPENVMS:
+			printf("Open VMS ABI\n");
+			break;
+		case ELFOSABI_NSK:
+			printf("Hewlett-Packard Non-Stop Kernel ABI\n");
+			break;
+		case ELFOSABI_AROS:
+			printf("Amiga Research OS ABI\n");
+			break;
+		case ELFOSABI_FENIXOS:
+			printf("The FenixOS highly scalable multi-core OS ABI\n");
+			break;
+		case ELFOSABI_CLOUDABI:
+			printf("Nuxi CloudABI ABI\n");
+			break;
+		case ELFOSABI_OPENVOS:
+			printf("Stratus Technologies OpenVOS ABI\n");
+			break;
+		default:
+			printf("Reserved ABI (%d)\n", bytes[EI_ABIVERSION]);
+			break;
+	}
+
+	printf("ABI Version: %d\n", bytes[EI_ABIVERSION]);
+
+	switch(bytes[EI_NIDENT] + bytes[EI_NIDENT + 1])
+	{
+		case ET_None:
+			printf("No file type\n");
+			break;
+		case ET_Rel:
+			printf("Rel\n");
+			break;
+		case ET_Exec:
+			printf("Exec\n");
+			break;
+		case ET_Dyn:
+			printf("File type is DYN (Position-Independent Executable file)\n");
+			break;
+		case ET_Core:
+			printf("Core\n");
+			break;
+		case ET_LOProc:
+			printf("LO\n");
+			break;
+		case ET_HIProc:
+			printf("HI\n");
+			break;
+		default:
+			fprintf(stderr, "Unknown file type\n");
+			return 1;
+	}
+
+	switch (bytes[EI_NIDENT + 2] + bytes[EI_NIDENT + 3]) {
+		case EM_860:
+			printf("Intel 80860\n");
+			break;
+		default:
+			fprintf(stderr, "Failed to identify machine type\n");
+			return 1;
+	}
+
+	printf("Read %ld bytes from file '%s'\n", size, argv[1]);
 }