diff --git a/app.cpp b/app.cpp
index e93df66..07d8729 100644
--- a/app.cpp
+++ b/app.cpp
@@ -62,7 +62,7 @@ GymLogDbParsed *parseDb(Arena *arena, string database) {
 
 list<GymLogEntry> loadEntryLog(Arena *arena, string fileLocation) {
     list<GymLogEntry> result = {0};
-    string logfile = readEntireFile(arena, LOG_FILE_LOCATION);
+    string logfile = os_readEntireFile(arena, LOG_FILE_LOCATION);
 
     if (logfile.length % sizeof(GymLogEntry) != 0) {
         log("Log file corrupted.\n");
@@ -96,7 +96,7 @@ WorkSummary workSummaryForExercise(list<GymLogEntry> entries) {
 
 int gymTrackerWorkToday(Arena *arena, uint32 exerciseId, string exerciseName) {
     int statusCode = 0;
-    string logfile = readEntireFile(arena, LOG_FILE_LOCATION);
+    string logfile = os_readEntireFile(arena, LOG_FILE_LOCATION);
 
     if (logfile.length % sizeof(GymLogEntry) != 0) {
         log("Log file corrupted.\n");
@@ -114,7 +114,7 @@ int gymTrackerWorkToday(Arena *arena, uint32 exerciseId, string exerciseName) {
             Timestamp logTs = timestampFromUnixTime(&logEntry.timestamp);
             if (logTs.tm_yday == todayTs.tm_yday && todayTs.tm_year == logTs.tm_year) {
                 todaysEntries.head += 1;
-                todaysEntries.data = &logEntries.data[i + 1];
+                todaysEntries.data = &logEntries.data[i];
             }
         }
 
@@ -131,9 +131,9 @@ int gymTrackerWorkToday(Arena *arena, uint32 exerciseId, string exerciseName) {
 
 int gymTrackerStatus(Arena *arena, list<string> args) {
     int statusCode = 0;
-    string file = readEntireFile(arena, LOG_FILE_LOCATION);
+    string file = os_readEntireFile(arena, LOG_FILE_LOCATION);
 
-    GymLogDbParsed *db = parseDb(arena, readEntireFile(arena, DB_FILE_LOCATION));
+    GymLogDbParsed *db = parseDb(arena, os_readEntireFile(arena, DB_FILE_LOCATION));
 
     if (file.length % sizeof(GymLogEntry) != 0) {
         puts("Log file corrupted.");
@@ -271,7 +271,7 @@ int gymTrackerDeleteEntries(Arena *arena, list<string> args) {
                 log("%i is more than the current number of log entries (%i). Aborting.", numToDelete, logEntries.length);
                 statusCode = 1;
             } else {
-                writeEntireFile(arena, LOG_FILE_LOCATION, (byte *)logEntries.data, (logEntries.length - numToDelete) * sizeof(GymLogEntry));
+                os_writeEntireFile(arena, LOG_FILE_LOCATION, (byte *)logEntries.data, (logEntries.length - numToDelete) * sizeof(GymLogEntry));
             }
         } else {
             log("Invalid number to delete.\n");
@@ -296,7 +296,7 @@ int gymTrackerDo(Arena *arena, list<string> args) {
     GymLogDbParsedEntry *existingEntry = 0;
 
     if (statusCode == 0) {
-        GymLogDbParsed *db = parseDb(arena, readEntireFile(arena, DB_FILE_LOCATION));
+        GymLogDbParsed *db = parseDb(arena, os_readEntireFile(arena, DB_FILE_LOCATION));
         for (EachIn(db->entries, i)) {
             GymLogDbParsedEntry entry = db->entries.data[i];
             if (strStartsWith(entry.name, newExerciseName)) {
@@ -327,7 +327,7 @@ int gymTrackerDo(Arena *arena, list<string> args) {
                 kg,
             };
 
-            fileAppend(arena, LOG_FILE_LOCATION, (byte *)&entry, sizeof(entry));
+            os_fileAppend(arena, LOG_FILE_LOCATION, (byte *)&entry, sizeof(entry));
             statusCode = gymTrackerWorkToday(arena, exerciseId, newExerciseName);
         }
     }
@@ -337,7 +337,7 @@ int gymTrackerDo(Arena *arena, list<string> args) {
 
 int gymTrackerListExercises(Arena *arena, list<string> args) {
     int statusCode = 0;
-    GymLogDbParsed *db = parseDb(arena, readEntireFile(arena, DB_FILE_LOCATION));
+    GymLogDbParsed *db = parseDb(arena, os_readEntireFile(arena, DB_FILE_LOCATION));
 
     if (db->entries.length == 0) {
         log("No entries currently registered in the exercise database.");
@@ -353,7 +353,7 @@ int gymTrackerListExercises(Arena *arena, list<string> args) {
 
 int gymTrackerAddExercise(Arena *arena, list<string> args) {
     int statusCode = 0;
-    GymLogDbParsed *db = parseDb(arena, readEntireFile(arena, DB_FILE_LOCATION));
+    GymLogDbParsed *db = parseDb(arena, os_readEntireFile(arena, DB_FILE_LOCATION));
 
     string newExerciseName = args.data[0];
     if (newExerciseName.length == 0) {
@@ -363,7 +363,7 @@ int gymTrackerAddExercise(Arena *arena, list<string> args) {
 
     if (statusCode != 1) {
         string databaseLocation = DB_FILE_LOCATION;
-        string database = readEntireFile(arena, databaseLocation);
+        string database = os_readEntireFile(arena, databaseLocation);
 
         byte *buf = 0; 
         size_t newEntryStartIndex = 0;
@@ -411,7 +411,7 @@ int gymTrackerAddExercise(Arena *arena, list<string> args) {
             byte *newExerciseNameDb = buf + newEntryStartIndex + sizeof(GymLogDbEntry);
             memcpy(newExerciseNameDb, newExerciseName.str, newExerciseName.length);
             size_t bufSize = newEntryStartIndex + sizeof(GymLogDbEntry) + newExerciseName.length;
-            writeEntireFile(arena, databaseLocation, buf, bufSize);
+            os_writeEntireFile(arena, databaseLocation, buf, bufSize);
         }
     }
 
@@ -430,16 +430,19 @@ int main(int argc, char **argv) {
     }
 
     if (statusCode == 0) {
-        if (strEql(args.data[0], "status"_s)) {
-            statusCode = gymTrackerStatus(arena, listSlice(args, 1));
-        } else if (strEql(args.data[0], "do"_s)) {
-            statusCode = gymTrackerDo(arena, listSlice(args, 1));
-        } else if (strEql(args.data[0], "delete"_s)) {
-            statusCode = gymTrackerDeleteEntries(arena, listSlice(args, 1));
-        } else if (strEql(args.data[0], "list"_s)) {
-            statusCode = gymTrackerListExercises(arena, listSlice(args, 1));
-        } else if (strEql(args.data[0], "add"_s)) {
-            statusCode = gymTrackerAddExercise(arena, listSlice(args, 1));
+        string cmd = args.data[0];
+        list<string> argsRest = listSlice(args, 1);
+
+        if (strEql("status"_s, cmd)) {
+            statusCode = gymTrackerStatus(arena, argsRest);
+        } else if (strEql("do"_s, cmd)) {
+            statusCode = gymTrackerDo(arena, argsRest);
+        } else if (strEql("delete"_s, cmd)) {
+            statusCode = gymTrackerDeleteEntries(arena, argsRest);
+        } else if (strEql("list"_s, cmd)) {
+            statusCode = gymTrackerListExercises(arena, argsRest);
+        } else if (strEql("add"_s, cmd)) {
+            statusCode = gymTrackerAddExercise(arena, argsRest);
         } else {
             log("Unknown command \"%S\"\n", args.data[0]);
             statusCode = 1;
diff --git a/build b/build
index 2c9057c..876340a 100755
--- a/build
+++ b/build
@@ -1,3 +1,3 @@
 #!/bin/bash
 
-g++ -g -g3 -DOS_LINUX ./app.cpp -o ./target/app
+g++ -Wall -g -g3 -DOS_LINUX ./app.cpp -o ./target/app
diff --git a/djstdlib/core.cpp b/djstdlib/core.cpp
index 12956e9..c08b51b 100644
--- a/djstdlib/core.cpp
+++ b/djstdlib/core.cpp
@@ -328,96 +328,14 @@ real32 parsePositiveReal32(string str, size_t *lengthPointer) {
     return result;
 }
 
-string readEntireFile(Arena *arena, string filename) {
-#if OS_WINDOWS
-    string result = {0};
-    HANDLE fileHandle = CreateFileA(cstring(arena, filename), GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, NULL, NULL);
-    if (fileHandle != INVALID_HANDLE_VALUE) {
-        LARGE_INTEGER fileSize;
-        if (GetFileSizeEx(fileHandle, &fileSize)) {
-            string readfile = PushString(arena, (size_t)fileSize.QuadPart);
-            if (readfile.str) {
-                DWORD bytesRead;
-                if (ReadFile(fileHandle, readfile.str, (DWORD)fileSize.QuadPart, &bytesRead, NULL) && (fileSize.QuadPart == bytesRead)) {
-                    result = readfile;
-                }
-            }
-        }
-        CloseHandle(fileHandle);
-    }
-    return result;
-#elif OS_LINUX
-    FILE *input = fopen((char *)filename.str, "r");
-    string readBuffer;
-    if (input) {
-        struct stat st;
-        stat((char *)filename.str, &st);
-        size_t fsize = st.st_size;
-        readBuffer = PushString(arena, fsize);
-        fread(readBuffer.str, sizeof(byte), readBuffer.length, input);
-        fclose(input);
-    } else {
-        readBuffer = PushString(arena, 0);
-    }
-    return readBuffer;
-#endif
-}
-
-bool writeEntireFile(Arena *arena, string filename, const byte *contents, size_t contentsLength) {
-    bool result = false;
-#if OS_WINDOWS
-    HANDLE fileHandle = CreateFileA(cstring(arena, filename), GENERIC_WRITE, FILE_SHARE_READ, NULL, CREATE_ALWAYS, NULL, NULL);
-    if (fileHandle != INVALID_HANDLE_VALUE) {
-        DWORD bytesWritten;
-        if (WriteFile(fileHandle, contents, (DWORD)contentsLength, &bytesWritten, NULL)) {
-            // file written successfully
-            result = bytesWritten == contentsLength;
-        }  
-        CloseHandle(fileHandle);
-    }  
-#elif OS_LINUX
-    FILE *output = fopen((char *)filename.str, "w");
-    if (output) {
-        fwrite(contents, contentsLength, contentsLength, output);
-        fclose(output);
-        result = true;
-    }
-#endif
-    return result;
-}
-
-bool fileAppend(Arena *arena, string filename, const byte *contents, size_t contentsLength) {
-    bool result = false;
-#if OS_WINDOWS
-    HANDLE fileHandle = CreateFileA(cstring(arena, filename), FILE_APPEND_DATA | FILE_GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
-    if (fileHandle != INVALID_HANDLE_VALUE) {
-        DWORD bytesWritten;
-        DWORD position = SetFilePointer(fileHandle, 0, NULL, FILE_END);
-        if (WriteFile(fileHandle, contents, (DWORD)contentsLength, &bytesWritten, NULL)) {
-            // file written successfully
-            result = bytesWritten == contentsLength;
-        }
-        CloseHandle(fileHandle);
-    }
-#elif OS_LINUX
-    FILE *output = fopen((char *)filename.str, "a");
-    if (output) {
-        fwrite(contents, contentsLength, contentsLength, output);
-        fclose(output);
-        result = true;
-    }
-#endif
-    return result;
-}
-
 list<string> getArgs(Arena *arena, int argc, char **argv) {
-    list<string> args = PushList(arena, string, (size_t)argc);
+    list<string> args = PushList(arena, string, (size_t)argc - 1);
     for (int i = 1; i < argc; i++) {
         appendList(&args, strFromCString(arena, argv[i]));
     }
     return args;
 }
-
+ 
 UnixTimestamp getSystemUnixTime() {
     time_t now;
     time(&now);
@@ -425,8 +343,9 @@ UnixTimestamp getSystemUnixTime() {
 }
 
 Timestamp timestampFromUnixTime(UnixTimestamp *unixTimestamp) {
-    tm *timestamp = gmtime((time_t *)unixTimestamp);
-    return *timestamp;
+    tm timestamp = {0};
+    gmtime_r((time_t *)unixTimestamp, &timestamp);
+    return timestamp;
 }
 
 string formatTimeHms(Arena *arena, UnixTimestamp time) {
@@ -459,65 +378,24 @@ string formatTimeYmd(Arena *arena, Timestamp *time) {
     return buf;
 }
 
-function void __core_log(LogTarget target, const char *fmt, va_list argList) {
-    Scratch scratch = scratchStart(0, 0);
-    string result = strPrintfv(scratch.arena, fmt, argList);
-#if OS_WINDOWS
-    DWORD done;
-    HANDLE stdHandle;
-    switch (target) {
-        case LogTarget_stdin: 
-            stdHandle = GetStdHandle(STD_INPUT_HANDLE);
-            break;
-        case LogTarget_stdout: 
-            stdHandle = GetStdHandle(STD_ERROR_HANDLE);
-            break;
-        case LogTarget_stderr: 
-            stdHandle = GetStdHandle(STD_OUTPUT_HANDLE);
-            break;
-        default:
-            stdHandle = GetStdHandle(STD_OUTPUT_HANDLE);
-            break;
-    }
-    WriteFile(stdHandle, result.str, (DWORD)result.length, &done, 0);
-#elif OS_LINUX
-    // TODO(djledda): finish implementation without cstdlib
-    switch (target) {
-        case LogTarget_stdin: 
-            write(0, (const void *)result.str, result.length);
-            break;
-        case LogTarget_stderr: 
-            fflush(stderr);
-            write(2, (const void *)result.str, result.length);
-            break;
-        case LogTarget_stdout: 
-        default:
-            fflush(stdout);
-            write(1, (const void *)result.str, result.length);
-            break;
-    }
-#endif
-    scratchEnd(scratch);
-}
-
 void logErr(const char *fmt, ...) {
     va_list argList;
     va_start(argList, fmt);
-    __core_log(LogTarget_stdout, fmt, argList);
+    os_log(LogTarget_stdout, fmt, argList);
     va_end(argList);
 }
 
 function void logStdout(const char *fmt, ...) {
     va_list argList;
     va_start(argList, fmt);
-    __core_log(LogTarget_stdout, fmt, argList);
+    os_log(LogTarget_stdout, fmt, argList);
     va_end(argList);
 }
 
 void log(const char *fmt, ...) {
     va_list argList;
     va_start(argList, fmt);
-    __core_log(LogTarget_stdout, fmt, argList);
+    os_log(LogTarget_stdout, fmt, argList);
     va_end(argList);
 }
 
diff --git a/djstdlib/core.h b/djstdlib/core.h
index 3654df1..2889d13 100644
--- a/djstdlib/core.h
+++ b/djstdlib/core.h
@@ -181,11 +181,6 @@ real32 parsePositiveReal32(Arena *arena, string str, size_t *lengthPointer);
 
 inline function bool isNumeric(char c); 
 
-// ### File IO ###
-string readEntireFile(Arena *arena, string filename); 
-bool writeEntireFile(Arena *arena, string filename, const byte *contents, size_t contentsLength); 
-bool fileAppend(Arena *arena, string filename, const byte *contents, size_t contentsLength); 
-
 // ### Cmdline ###
 list<string> getArgs(Arena *arena, int argc, char **argv); 
 
diff --git a/djstdlib/os.h b/djstdlib/os.h
index 44aac28..07b654e 100644
--- a/djstdlib/os.h
+++ b/djstdlib/os.h
@@ -9,4 +9,12 @@ void os_reserve(void *ptr);
 void os_decommit(void *ptr);
 void os_free(void *ptr, size_t freeSize);
 
+// ### File IO ###
+string os_readEntireFile(Arena *arena, string filename); 
+bool os_writeEntireFile(Arena *arena, string filename, const byte *contents, size_t contentsLength); 
+bool os_fileAppend(Arena *arena, string filename, const byte *contents, size_t contentsLength); 
+
+// ### Standard IO ###
+void os_log(LogTarget target, const char *fmt, va_list argList);
+
 #endif
diff --git a/djstdlib/os_linux.cpp b/djstdlib/os_linux.cpp
index 01f9330..3add835 100644
--- a/djstdlib/os_linux.cpp
+++ b/djstdlib/os_linux.cpp
@@ -22,4 +22,63 @@ void os_free(void *ptr, size_t size) {
     Assert(err != -1);
 }
 
+string os_readEntireFile(Arena *arena, string filename) {
+    FILE *input = fopen((char *)filename.str, "r");
+    string readBuffer;
+    if (input) {
+        struct stat st;
+        stat((char *)filename.str, &st);
+        size_t fsize = st.st_size;
+        readBuffer = PushString(arena, fsize);
+        fread(readBuffer.str, sizeof(byte), readBuffer.length, input);
+        fclose(input);
+    } else {
+        readBuffer = PushString(arena, 0);
+    }
+    return readBuffer;
+}
+
+bool os_writeEntireFile(Arena *arena, string filename, const byte *contents, size_t contentsLength) {
+    bool result = false;
+    FILE *output = fopen((char *)filename.str, "w");
+    if (output) {
+        fwrite(contents, contentsLength, contentsLength, output);
+        fclose(output);
+        result = true;
+    }
+    return result;
+}
+
+bool os_fileAppend(Arena *arena, string filename, const byte *contents, size_t contentsLength) {
+    bool result = false;
+    FILE *output = fopen((char *)filename.str, "a");
+    if (output) {
+        fwrite(contents, sizeof(byte), contentsLength, output);
+        fclose(output);
+        result = true;
+    }
+    return result;
+}
+
+void os_log(LogTarget target, const char *fmt, va_list argList) {
+    Scratch scratch = scratchStart(0, 0);
+    string result = strPrintfv(scratch.arena, fmt, argList);
+    // TODO(djledda): finish implementation without cstdlib
+    switch (target) {
+        case LogTarget_stdin: 
+            write(0, (const void *)result.str, result.length);
+            break;
+        case LogTarget_stderr: 
+            fflush(stderr);
+            write(2, (const void *)result.str, result.length);
+            break;
+        case LogTarget_stdout: 
+        default:
+            fflush(stdout);
+            write(1, (const void *)result.str, result.length);
+            break;
+    }
+    scratchEnd(scratch);
+}
+
 #endif
diff --git a/djstdlib/os_win32.cpp b/djstdlib/os_win32.cpp
index a255c8a..70ba555 100644
--- a/djstdlib/os_win32.cpp
+++ b/djstdlib/os_win32.cpp
@@ -18,4 +18,75 @@ void os_free(void *ptr, size_t size) {
     VirtualFree(ptr, NULL, MEM_RELEASE);
 }
 
+string os_readEntireFile(Arena *arena, string filename) {
+    string result = {0};
+    HANDLE fileHandle = CreateFileA(cstring(arena, filename), GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, NULL, NULL);
+    if (fileHandle != INVALID_HANDLE_VALUE) {
+        LARGE_INTEGER fileSize;
+        if (GetFileSizeEx(fileHandle, &fileSize)) {
+            string readfile = PushString(arena, (size_t)fileSize.QuadPart);
+            if (readfile.str) {
+                DWORD bytesRead;
+                if (ReadFile(fileHandle, readfile.str, (DWORD)fileSize.QuadPart, &bytesRead, NULL) && (fileSize.QuadPart == bytesRead)) {
+                    result = readfile;
+                }
+            }
+        }
+        CloseHandle(fileHandle);
+    }
+    return result;
+}
+
+bool os_writeEntireFile(Arena *arena, string filename, const byte *contents, size_t contentsLength) {
+    bool result = false;
+    HANDLE fileHandle = CreateFileA(cstring(arena, filename), GENERIC_WRITE, FILE_SHARE_READ, NULL, CREATE_ALWAYS, NULL, NULL);
+    if (fileHandle != INVALID_HANDLE_VALUE) {
+        DWORD bytesWritten;
+        if (WriteFile(fileHandle, contents, (DWORD)contentsLength, &bytesWritten, NULL)) {
+            // file written successfully
+            result = bytesWritten == contentsLength;
+        }  
+        CloseHandle(fileHandle);
+    }  
+    return result;
+}
+
+bool os_fileAppend(Arena *arena, string filename, const byte *contents, size_t contentsLength) {
+    bool result = false;
+    HANDLE fileHandle = CreateFileA(cstring(arena, filename), FILE_APPEND_DATA | FILE_GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
+    if (fileHandle != INVALID_HANDLE_VALUE) {
+        DWORD bytesWritten;
+        DWORD position = SetFilePointer(fileHandle, 0, NULL, FILE_END);
+        if (WriteFile(fileHandle, contents, (DWORD)contentsLength, &bytesWritten, NULL)) {
+            // file written successfully
+            result = bytesWritten == contentsLength;
+        }
+        CloseHandle(fileHandle);
+    }
+    return result;
+}
+
+function void os_log(LogTarget target, const char *fmt, va_list argList) {
+    Scratch scratch = scratchStart(0, 0);
+    string result = strPrintfv(scratch.arena, fmt, argList);
+    DWORD done;
+    HANDLE stdHandle;
+    switch (target) {
+        case LogTarget_stdin: 
+            stdHandle = GetStdHandle(STD_INPUT_HANDLE);
+            break;
+        case LogTarget_stdout: 
+            stdHandle = GetStdHandle(STD_ERROR_HANDLE);
+            break;
+        case LogTarget_stderr: 
+            stdHandle = GetStdHandle(STD_OUTPUT_HANDLE);
+            break;
+        default:
+            stdHandle = GetStdHandle(STD_OUTPUT_HANDLE);
+            break;
+    }
+    WriteFile(stdHandle, result.str, (DWORD)result.length, &done, 0);
+    scratchEnd(scratch);
+}
+
 #endif