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File opened successfully. Contents: String: 111 222 3String: 33String: 444 555 6String: 66 String: 777 888 9String: 99Now closing file...

The main area of focus is the while loop - notice how I performed the check for the return of a NULL pointer. Remember that passing in char * variable, c as the first argument assigns the line read into c, which is printed off by printf. We specified a maximum number of characters to be 10 - we knew the number of characters per line in our text file is more than this, but we wanted to show that fgets reads 10 characters at a time in this case.

Notice how fgets returns when the newline character is reached - this would explain why 444 and 777 follow the word "String". Also, the tab character, \t, is treated as one character.

Other function:

Fseek() function

int fseek (FILE *fp, long int offset, int origin);

In the above prototype, there are two arguments:

  • fp: Pointer to a FILE object that identifies the stream.
  • offset: Number of bytes to offset from origin.
  • If offset>= 0: set the position indicator toward to the end of file,
  • If offset<0: set the position indicator toward to the beginning of file.
  • origin: Position from where offset is added. It is specified by one of the following constants defined in<cstdio>:
Constant Value Meaning
SEEK_SET 0 Beginning of file
SEEK_CUR 1 Current position of the file pointer
SEEK_END 2 End of file

This function sets the position indicator associated with the fp to a new position defined by adding offset to a reference position specified by origin. The End-of-File internal indicator of the file is cleared after a call to this function.

Return Value: If successful, the function returns a zero value. Otherwise, it returns nonzero value.

#include<stdio.h>int main () {FILE * fp; fp = fopen ( "myfile.txt" , "w" );fputs ( "This is an apple." , fp ); fseek ( fp , -8 , SEEK_END );fputs ( " sam" , fp ); fclose ( fp );return 0; }
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After this code is successfully executed, the file myfile.txt contains:

This is a sample.
#include<stdio.h>int main () {FILE * fp; fp = fopen ( "myfile.txt" , "w" );fputs ( "This is an apple." , fp ); fseek ( fp , 9 , SEEK_SET );fputs ( " sam" , fp ); fclose ( fp );return 0; }
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After this code is successfully executed, the file myfile.txt contains:

This is a sample.

Rewind() function

void rewind (FILE *fp);

This function sets the current position indicator associated with fp to the beginning of the file. A call to rewind is equivalent to:

fseek (fp, 0, SEEK_SET);

except that, unlike fseek, rewind clears the error indicator.

On streams open for update (read+write), a call to rewind allows to switch between reading and writing.

#include<stdio.h>#include<conio.h>int main () {char str [80];int n; FILE * fp;fp = fopen ("myfile.txt","w+"); for ( n='A' ; n<='Z' ; n++) fputc ( n, fp);rewind (fp); n=0;while (!feof(fp)) {str[n]= fgetc(fp);n++; }fclose (fp); printf ("I have read: %s \n",str);getch(); return 0;}
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A file called myfile.txt is created for reading and writing and filled with the alphabet. The file is then rewinded, read and its content is stored in a buffer, that then is written to the standard output:

Questions & Answers

do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Introduction to computer science. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10776/1.1
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