File Handling. Reference:

Transcription

1 File Handling Reference:

2 Array argument return int * getrandom( ) static int r[10]; int i; /* set the seed */ srand( (unsigned)time( NULL ) ); for ( i = 0; i < 10; ++i) r[i] = rand(); printf( "r[%d] = %d\n", i, r[i]); int main () /* a pointer to an int */ int *p; int i; p = getrandom(); for ( i = 0; i < 10; i++ ) printf( "*(p + %d) : %d\n", i, *(p + i)); return r; return 0;

3 getc() int getc(file *stream) #include<stdio.h> int main() char c; printf("enter character: "); c = getc(stdin); printf("character entered: "); putc(c, stdout);

4 putc() int putc(int char, FILE *stream) char -- This is the character to be written. The character is passed as its int promotion. stream -- This is the pointer to a FILE object that identifies the stream where the character is to be written. int main () FILE *fp; int ch; fp = fopen("file.txt", "w"); for( ch = 33 ; ch <= 100; ch++ ) putc(ch, fp);

5 gets() char *gets(char *str) int main() char str[50]; printf("enter a string : "); gets(str); printf("you entered: %s", str);

6 puts() int puts(const char *str) #include <string.h> int main() char str1[15]; char str2[15]; strcpy(str1, "tutorialspoint"); strcpy(str2, "compileonline"); puts(str1); puts(str2);

7 char *fgets(char *str, int n, FILE *stream) fgets() str -- This is the pointer to an array of chars where the string read is stored. n -- This is the maximum number of characters to be read (including the final null-character). Usually, the length of the array passed as str is used. stream -- This is the pointer to a FILE object that identifies the stream where characters are read from. int main() FILE *fp; char str[60]; fp = fopen("file.txt", "r"); if(fp == NULL) perror("error opening file"); return(-1); if( fgets (str, 60, fp)!=null ) puts(str);

8 fputs() int fputs(const char *str, FILE *stream) str -- This is an array containing the null-terminated sequence of characters to be written. stream -- This is the pointer to a FILE object that identifies the stream where the string is to be written. int main () FILE *fp; fp = fopen("file.txt", "w+"); fputs("this is c programming.", fp); fputs("this is a system programming language.", fp);

9 fprintf() int fprintf(file *stream, const char *format,...) stream -- This is the pointer to a FILE object that identifies the stream. format -- This is the C string that contains the text to be written to the stream.it can optionally contain embedded format tags that are replaced by the values specified in subsequent additional arguments and formatted as requested. Format tags prototype is % [flags][width][.precision][length]specifier, which is explained below: #include <stdlib.h> int main() FILE * fp; fp = fopen ("file.txt", "w+"); fprintf(fp, "%s %s %s %d", "We", "are", "in", 2012);

10 int fscanf(file *stream, const char *format,...) fscanf() stream -- This is the pointer to a FILE object that identifies the stream. format -- This is the C string that contains one or more of the following items: Whitespace character, Non-whitespace character and Format specifiers. A format specifier will be as [=%[*][width][modifiers]type=], which is explained below: #include <stdlib.h> int main() char str1[10], str2[10], str3[10]; int year; FILE * fp; fp = fopen ("file.txt", "w+"); fputs("we are in 2012", fp); rewind(fp); fscanf(fp, "%s %s %s %d", str1, str2, str3, &year); printf("read String1 %s \n", str1 ); printf("read String2 %s \n", str2 ); printf("read String3 %s \n", str3 ); printf("read Integer %d \n", year );

11 fread() size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream) ptr -- This is the pointer to a block of memory with a minimum size of size*nmemb bytes. size -- This is the size in bytes of each element to be read. nmemb -- This is the number of elements, each one with a size of size bytes. stream -- This is the pointer to a FILE object that specifies an input stream. #include <string.h> int main() FILE *fp; char c[] = "this is tutorialspoint"; char buffer[20]; /* Open file for both reading and writing */ fp = fopen("file.txt", "w+"); /* Write data to the file */ fwrite(c, strlen(c) + 1, 1, fp); /* Seek to the beginning of the file */ fseek(fp, SEEK_SET, 0); /* Read and display data */ fread(buffer, strlen(c)+1, 1, fp); printf("%s\n", buffer);

12 fwrite() size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream) ptr -- This is the pointer to the array of elements to be written. size -- This is the size in bytes of each element to be written. nmemb -- This is the number of elements, each one with a size of size bytes. stream -- This is the pointer to a FILE object that specifies an output stream. #include<stdio.h> int main () FILE *fp; char str[] = "This is tutorialspoint.com"; fp = fopen( "file.txt", "w" ); fwrite(str, 1, sizeof(str), fp );

13 fseek() int fseek(file *stream, long int offset, int whence) stream -- This is the pointer to a FILE object that identifies the stream. offset -- This is the number of bytes to offset from whence. whence -- This is the position from where offset is added. It is specified by one of the following constants: SEEK_SETB -eginning of file SEEK_CUR -Current position of the file pointer SEEK_END - End of file int main () FILE *fp; fp = fopen("file.txt","w+"); fputs("this is tutorialspoint.com", fp); fseek( fp, 7, SEEK_SET ); fputs(" C Programming Langauge", fp);

14 void rewind(file *stream) rewind() int main() FILE *fp; int ch; fp = fopen("file.txt", "r"); if( fp!= NULL ) while(!feof(fp) ) ch = fgetc(fp); printf("%c", ch); rewind(fp); while(!feof(fp) ) ch = fgetc(fp); printf("%c", ch); This is tutorialspoint.com This is tutorialspoint.com

15 long int ftell(file *stream) int main () FILE *fp; int len; fp = fopen("file.txt", "r"); if( fp == NULL ) perror ("Error opening file"); return(-1); fseek(fp, 0, SEEK_END); len = ftell(fp); printf("total size of file.txt = %d bytes\n", len); File: This is tutorialspoint.com Total size of file.txt = 27 bytes ftell()

16 int fclose(file *fp); getw() integer read putw() integer write fflush() Others

17 Command Line Arguments int main( int argc, char *argv[] ) if( argc == 2 ) printf("the argument supplied is %s\n", argv[1]); else if( argc > 2 ) printf("too many arguments supplied.\n"); else printf("one argument expected.\n");

18 Thank You