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Top Forums Programming Correct way to read data of different formats into same struct Post 302940615 by yifangt on Tuesday 7th of April 2015 04:47:52 PM
Old 04-07-2015
Thanks Don:
I am aware what you meant by fgets() + sscanf() + strncpy() to parse input. At this moment I am working with fscanf() and assuming no missing field of the data.
According to this reference:
Code:
int fscanf ( FILE * stream, const char * format, ... );
Reads data from the stream and stores them according to the parameter format into the locations pointed by the additional arguments.
......
On success, the function returns the number of items of the argument list successfully filled.

My unclear part is: can the number of items of the argument list be separated by newline, i.e. in different rows? In other words, fscanf() keeps looking for the defined items until all of them are found, no matter those items are separated by space, tab or newline?
To give more of my confusion by this code fragment:
Code:
  rewind (pFile);                  //Line 11
  fscanf (pFile, "%f", &f);        //Line 12
  fscanf (pFile, "%s", str);       //Line 13

Line 11: set position of pFile stream to the beginning
Line 12: Look for a float number in one line (e.g. line 1)
Line 13: Look for a string in next line(line 2), or the same line(line 1)?
Code:
  rewind (pFile);                          //Line 11
  fscanf (pFile, "%f %s", &f, str);        //Line 12

This time Line 12 would be Looking for a float number AND a string in the same line (line 1)?
Sorry for this naive question, which bugs me. Thanks a lot!

Last edited by yifangt; 04-07-2015 at 06:10 PM..
 

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gets(3C)						   Standard C Library Functions 						  gets(3C)

NAME
gets, fgets - get a string from a stream SYNOPSIS
#include <stdio.h> char *gets(char *s); char *fgets(char *s, int n, FILE *stream); DESCRIPTION
The gets() function reads bytes from the standard input stream (see intro(3)), stdin, into the array pointed to by s, until a newline char- acter is read or an end-of-file condition is encountered. The newline character is discarded and the string is terminated with a null byte. If the length of an input line exceeds the size of s, indeterminate behavior may result. For this reason, it is strongly recommended that gets() be avoided in favor of fgets(). The fgets() function reads bytes from the stream into the array pointed to by s, until n-1 bytes are read, or a newline character is read and transferred to s, or an end-of-file condition is encountered. The string is then terminated with a null byte. The fgets() and gets() functions may mark the st_atime field of the file associated with stream for update. The st_atime field will be marked for update by the first successful execution of fgetc(3C), fgets(), fread(3C), fscanf(3C), getc(3C), getchar(3C), gets(), or scanf(3C) using stream that returns data not supplied by a prior call to ungetc(3C) or ungetwc(3C). RETURN VALUES
If end-of-file is encountered and no bytes have been read, no bytes are transferred to s and a null pointer is returned. For standard-con- forming (see standards(5)) applications, if the end-of-file indicator for the stream is set, no bytes are transferred to s and a null pointer is returned whether or not the stream is at end-of-file. If a read error occurs, such as trying to use these functions on a file that has not been opened for reading, a null pointer is returned and the error indicator for the stream is set. If end-of-file is encoun- tered, the EOF indicator for the stream is set. Otherwise s is returned. ERRORS
Refer to fgetc(3C). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ SEE ALSO
lseek(2), read(2), ferror(3C), fgetc(3C), fgetwc(3C), fopen(3C), fread(3C), getchar(3C), scanf(3C), stdio(3C), ungetc(3C), ungetwc(3C), attributes(5), standards(5) SunOS 5.10 15 Oct 2003 gets(3C)
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