C Stdlib Notes

From Rebertia

Contents 1 stdlib.h 2 stdio.h 2.1 Basics 2.2 Low-level 2.3 Misc 2.4 Random access 2.5 Binary streams only 3 string.h

stdlib.h

All but free() return NULL on error.

• void* malloc(sizeInBytes)
• void* calloc(lengthOfArray, sizeOfArrayElement) - zeros memory beforehand
• void* realloc(void*, newSizeInBytes)
• void free(void*)

stdio.h

Basics

• FILE* fopen(filename, mode) - NULL on error
• FILE* freopen(filename, mode, FILE*) - used to redirect stdin, stdout, etc. NULL & closes file on error
• int fclose(FILE*) - EOF on error
• int fflush(FILE*) - EOF on error
• FOPEN_MAX - max # of files you can have open
• FILENAME_MAX - length of longest possible filename
• EOF - End Of File sentinel value
• int fputs(char[], FILE*) - EOF on error
• char[] fgets(char[] buffer, bufferSize, FILE*) - stops on newline (but will include it). returns NULL on error/EOF, otherwise returns buffer itself
• int fprintf(FILE*, format, ...) - # chars printed, or EOF on error
• int fscanf(FILE*, format, ...) - EOF on immediate error, # values assigned otherwise (< expected indicates error)

Low-level

• int getc(FILE*) - EOF on error
• int ungetc(char, FILE*) - EOF on error
• int putc(char, FILE*) - EOF on error

Misc

• int snprintf(char[] buffer, sizeOfBuffer, format, ...)
• int sscanf(char[] source, format, ...)
• bool ferror(FILE*) - check FILE's error flag
• bool feof(FILE*) - is position @ EOF?
• void clearerr(FILE*) - clears error+EOF flags

Random access

• long ftell(FILE*) - returns file position. on error, returns -1 and sets errno
• int fseek(FILE*, long offsetInBytes, origin) - returns -1 on error
  • origin values:
    • SEEK_SET - start of file
    • SEEK_CUR - current position
    • SEEK_END - EOF

NOTE: some things not actually ints in the preceding

Binary streams only

• int fread(void* object, sizeOfObject, numberOfObjects, FILE*) - reads object in from file. returns # of objs read; if < numberOfObjects, then error/EOF
• int fwrite(void* object, sizeOfObject, numberOfObjects, FILE*) - reads object in from file. returns # of objs written; if < numberOfObjects, then error/EOF

string.h

• char[] strerror(errno) - error message describing error