On Tue, 31 Jul 2007 18:00:03 +0400,
Андрій Мішковський wrote:
> Hi, Mateus.
> Maybe it looks rude, but i want to correct you: fread, feof, fopen are
> _not_ system calls, as i remember. Your example is correct, but it makes
> no use of system calls. Your code is pure ISO C. :)
> Considering this, the program should look like this:
>
> #include <unistd.h> /*read(), close()*/ #include <fcntl.h> /*open()*/
> #include <stdio.h> /*fprintf()*/
> #include <sys/types.h> /**/
> #include <errno.h> /* errno*/
> #include <string.h> /* strerror(), memset()*/
>
> int
> main(int argc, char **argv)
> {
> int fd; /*file descriptor*/
> char buf[BUFSIZ]; /*buffer for reading data*/ int bytes_read = -1;
> /*bytes, already read from file*/
>
> if (argc != 2)
> {
> fprintf(stderr, "Usage: %s <file>\n", argv[0]); return 1;
> }
>
> fd = open (argv[1], O_RDONLY);
> if (fd == -1)
> {
> fprintf(stderr, "%s: open() failed. Reason: %s", argv[0],
> strerror(errno)); return 1;
> }
>
> while (bytes_read != 0)
> {
> bytes_read = read(fd, buf, BUFSIZ);
> if (bytes_read == -1)
> {
> fprintf(stderr, "%s: read() failed. Reason: %s",
argv[0],
> strerror(errno)); close(fd);
> return 1;
> }
> fprintf(stdout, "%s", buf);
> memset(buf, 0, BUFSIZ);
> }
>
> close(fd);
>
> return 0;
> }
>
> 2007/7/31, Mateus Interciso <p.zarnick@xxxxxxxxx>:
>> On Tue, 31 Jul 2007 04:27:13 -0700, nisa wrote:
>>
>> > hi,
>> > i am quite new to programming using system calls and would like a
>> > basic idea regarding the usage of system calls. i would like
>> > assistance in the following area of c programming in linux: 1.how to
>> > open a text file ,read data and print the data on console using
>> > system calls
>> > 2.create a text file and write some data 3.read data from a file and
>> > append that data to another file using lseek() 4.creation of a parent
>> > and child process using fork()
>>
>> Well, just to not let you in blank, here is a VERY simple file that
>> reads a text file, and output it to the screen
>>
>> #include <stdio.h> //standard IO
>> #include <stdlib.h> //for reading files #include <string.h> //for
>> memset
>> #include <errno.h> //for errno
>> int main(int argc, char *argv[]){
>> FILE *fp = NULL;
>> char ch[1];
>>
>> if(argc!=2){
>> fprintf(stderr,"Usage:%s <file>\n",argv[0]); return 1;
>> }
>> memset(ch,'\0',sizeof(char)*1);
>> if((fp=fopen(argv[1],"r"))==NULL){
>> perror("fopen");
>> return errno;
>> }
>> while(feof(fp)==0){
>> if( (fread(ch,sizeof(char),1,fp)==0) && (feof(fp)==0) ){
>> perror("fread");
>> fclose(fp);
>> memset(ch,'\0',sizeof(char)*1);
>> return errno;
>> }
>> fprintf(stdout,"%c",ch[0]);
>> }
>> fclose(fp);
>> memset(ch,'\0',sizeof(char)*1);
>> return 0;
>> }
>>
>> Also, as it was stated before, use the man pages. If you don't have a
>> Linux box, then google will be your friend for this. In this example,
>> you would need, the man pages for fopen(),fread() and feof().
>>
>> Good luck.
>>
>> -
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>>
You are absolutly right, I'm terrible sorry...It's just that it has been
so long since I haven't used open(), read(), close(), that I must have
gone crazy, I'm terribly sorry for this.
Mateus
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