C语言讲义第七章.ppt

CHAPTER7：Input Output 26 int getc(FILE *fp) /*return the next character, if at the end of the file, will return EOF */ 返回文件中的下一个字符，如果到达文件末尾则返回EOF int putc(int c, FILE *fp) /*write the character c to the file fp and return the character put out */ 将字符c写入fp指向的文件，返回写入的字符 CHAPTER7：Input Output 27 the standard in stdin the standard out stdout the standard error stderr 标准输入输出设备被看作文件处理 #define getchar() getc(stdin) #define putchar(c) putc((c),stdout) CHAPTER7：Input Output 28 Formatted input and output for file int fscanf(FILE *fp, char *format, ...); int fprintf(FILE *fp, char *format, ...); fscanf(fp, %f %f %f %f, SFx, SFy, Kx, Ky); fprintf(fp, %f %f %f %f, SFx, SFy, Kx, Ky); CHAPTER7：Input Output 29 #include stdio.h main(int argc, char *argv[ ]) /* cat concatenate files*/ { FILE *fp; void filecopy(FILE *, FILE *); if(argc==1) filecopy(stdin,stdout); else while(--argc0) if((fp=fopen(*++argv,”r”))==NULL) { printf(“cat:can’t open %s\n”,*argv); return 1; } else { filecopy(fp,stdout); fclose(fp); } return 0; } cat x.c y.c CHAPTER7：Input Output 30 /* filecopy: copy file ifp to file ofp*/ void filecopy(FILE *ifp , FILE *ofp) { int c; while((c=getc(ifp))!=EOF) putc(c,ofp); } Note: stdin and stdout are objects of type FILE *, they are constants, not variables. CHAPTER7：Input Output 31 int fclose(FILE *fp) Note: To break the connection between the file ointer and the external name that was established by fopen. You can also close stdin and stdout if they are not needed. fclose(stdin); fclose(stdout); back CHAPTER7：Input Output 32 7.6 Error Handling-Stderr and Exit if the stdout is not the screen, so the error information will be invisible. stderr Note: output written on stderr normally appears on the screen even if the standard output is redirec