1CMSC 212 – S07 (lect 6)AnnouncementsProgram #2– Due two weeks from todayReading– Chapter 15 (today)• skip 15.10.1 and 15.10.2 (scanf)– Chapter 112CMSC 212 – S07 (lect 6)Project NotesStart Early! - It's longer than P1Helpful functions– int strncpy(char *s1, char *s2, int max);– size_t strspn(const char *, const char *);– size_t strcspn(const char *, const char *);– int isalnum(char);– void perror(char *message);– void exit(int status);Suggestions– Start simple• write command line argument code• write code to read input file• write code to parse and/or modify input line as needed• Test and add code in steps3CMSC 212 – S07 (lect 6)Printf (the rest of the story)int fprintf(FILE *stream, char *format, …);– sends output to streamprintf(char *format, …);– sends output to stdoutsnprintf(char *buffer, int limit, char *format, …);– sends output the the character buffer– prints at most limit-1 characters to buffer• adds null to end of stringnever! use sprintf (due to buffer overflow)4CMSC 212 – S07 (lect 6)Printf format codesc print argument as unsigned characterd print as decimal integeru print as unsigned integerx print as hex (use X for capital A-F in format)e print in exponent form (6.02300e23)f print in floating point formats print as a string (null terminated character array)% print a % (so %% prints one %)5CMSC 212 – S07 (lect 6)Printf – Flags and Field WidthsFlags– - left justify the field (default is right)– + for signed numbers force the + to be printed– #• For x and X ensures a leading 0x or 0XPrecision – How many characters will be printed– Format is x.y• For int types – x is total width and y is numeric digits– Leading 0’s are added to bring width up to y• For floating points numbers – X is total width and y is digits right of decimal point6CMSC 212 – S07 (lect 6)Format code examplesABCDEFGHABC..A….%-5sABCDE..ABC….A%5.5sABCDEABCA%.5sABCDEFGH..ABC….A%5sABCDEFGHABCA%sABCDEFGHABCAFormat Code+123456789+12345-12+1%+d12345678912345-0120001%04d12345678912345-12.1…%-4d123456789.12345.-0012..0001%6.4d12345678912345-00120001%.4d123456789.12345…-12…..1%6d12345678912345-121%d12345678912345-121Format7CMSC 212 – S07 (lect 6)Binary I/OWrite out data structures in raw format– Tends to be non-portablesize_t fread(void *buffer, size_t size, size_t count, FILE *stream);– Read into buffer, count items of size size from stream– Returns the number of items read– ret = fread(mystuff, sizeof(struct foo), 42, stdin);size_t fwrite(void *buffer , size_t size, size_t count, FILE *stream);– Write to stream, count items of size size starting at buffer– Return the number of items written8CMSC 212 – S07 (lect 6)Other FILE Operationsint fflush(FILE *fp);– Write any buffered output to the destinationlong ftell(FILE *stream);– Return the current position (offset) of the stream– Return value is in bytesint fseek(FILE *stream, long offset, int from);– Change the position of the stream– Where depends on value of from• SEEK_SET - offset bytes from start of file• SEEK_CUR - offset bytes from the current position• SEEK_END - offset bytes from the end of the file• Last two may be positive or negative9CMSC 212 – S07 (lect 6)Misc. FILE FunctionsError and Status– int feof(FILE *stream);• Returns true if currently at end of file– int ferror(FILE *stream);• Returns true if any error condition is true– void clearerr(FILE *stream);• Reset the error indication for the fileTemporary Files– Sometimes need a file that is temporary• But it needs to be unique– FILE *tmpfile(void);• Create a new file that, it will be deleted on close10CMSC 212 – S07 (lect 6)Make: A Tool to Compile ProgramsProblem: Compiling programs is tediousSolution: Automate it!Done in Unix by the make command– Uses a file called Makefile• A makefile is a file (script) containing :– Project structure (files, dependencies)– Instructions for files creationMake is not limited to C programsAdapted from: www.cs.tau.ac.il/~dcor/Software1/Makefile.ppt11CMSC 212 – S07 (lect 6)Describing Files to MakeMakefile contains project dependencies– represented as a DAG (= Directed Acyclic Graph) Example:– Program contains 3 files– main.c., sum.c, sum.h– sum.h included in both .c files– Executable should be the file sumsum (exe)sum.omain.osum.csum.hmain.c12CMSC 212 – S07 (lect 6)Makefile for Previous Examplesum: main.o sum.ogcc –o sum main.o sum.omain.o: main.c sum.hgcc –c main.c sum.o: sum.c sum.hgcc –c sum.c  Notes About Makefiles:– Target is first item in a dependency– Items after “:” required to build target– Actions must have a tab at start– First target in file is the default rootTarget DependencyTabAction13CMSC 212 – S07 (lect 6)Make’s OperationProject dependencies tree is constructedA target is out of date when one of its dependencies is newer than itself.If out of date, recreate the target– Perform action specified– Done on the way up the tree. Notes:– Ensures minimum compilation, with proper project structure– Avoid writing something like:prog: main.c sum1.c sum2.cgcc –o prog main.c sum1.c sum2.c• requires full compilation when something changes14CMSC 212 – S07 (lect 6)Additional Make FeaturesMacros– <variable> = <value>– Example:CC = gccCFLAGS = -g -WallFoo.o: foo.c$(CC) $(CFLAGS) –c foo.cDefault Action– $(CC) –c $(CFLAGS)Actions can sometimes delete files not create them– Example:Clean:rm *.o15CMSC 212 – S07 (lect 6)More Complex Makefileall: intCount tableclean:rm -f *.o *.bb *.bbg *.da *.pngintCount: intCount.o$(CC) -o intCount intCount.otable: table.o main.o hashTable.o$(CC) -o table table.o main.o hashTable.otable.o: table.c table.hhashTable.o: hashTable.c table.hmain.o: main.c table.hCC = gccCFLAGS = -g -WallTwo top-level programsLink together several filesUses Default RuleMacro DefinitionsNot part of main treebuilt by typing “make