Programming

Hello,

I am very new in writing low level programming in C. I am trying to get an output in Linux 2.6.17.6 gentoo platform, but I don't get any output.

I am trying to do the following:

I am trying to scan a word and print its content at the standard output by using sscanf and printf.

I am trying to read the cpuinfo at the /proc directory, which looks like as following, and then, I am trying to print the highlighted string.

cat cpuinfo

processor : 0
vendor_id : GenuineIntel
cpu family : 15
model : 2
model name : Intel(R) Celeron(R) CPU 2.60GHz
stepping : 9
cpu MHz : 2591.654
cache size : 128 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe up cid xtpr
bogomips : 5189.98

But, I can only print the model name but cannot print its concent.

My C file looks as below.

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>

main(int argc,char **argv) {
char mybuf[4256];
char vernum[116];
int fd;
int errs;
int count;

if (argc != 2) {
printf("Bad command line argument\n");
exit(-1);
}
if ((fd = open (argv[1],O_RDONLY))< 0){
perror("Bad open");
exit(-1);
}
while ((count = read(fd, &mybuf[0], sizeof(mybuf))) > 0) {
count = read(fd,&mybuf[0],sizeof(mybuf));
sscanf(&mybuf[0],"model name %s",&vernum[0]);
printf("The model name is:%s\n", &vernum[0]);
}
if(count < 0) {
perror ("Bad read");
exit (-1);
}
}

Please tell me what I shouls fix at sccaf( ) and at the printf( ) method. I tried a lot by reading the man page to read new line or empty space or \t and by putting %c or *. But I never cannot print anything after model name.

If you need, you can see the file "cpuinfo" at /proc directory. Type cd /proc
then cat cpuinfo.


Please help me; I am here for help as it is a help forum for new and unexperienced like me.

Please tell me what to do in the code and what to write....so that I can print the whole string "model name : Intel(R) Celeron(R) CPU 2.60GHz"

Thank you.
Sharmin

Hi Sharmin,

the simple way is

Code:

#include <stdio.h>
#include <string.h>


main(int argc, char *argv[])
{
    FILE *fp;
    char buf[256], *p;

    if(argc < 2){
	printf("Bad command line\n");
	exit(1);
    }
    if(NULL == (fp = fopen(argv[1], "rt"))){
	printf("Can't open %s\n", argv[1]);
	exit(1);
    }
    for(;fgets(buf, 255, fp);){
	if(buf == strstr(buf, "model name")){
	    if(NULL != (p = strchr(buf, ':')))
		printf("%s\n", p + 1);
	    break;
	}
    }
    fclose(fp);

    return 0;
}

Hello,

thank you.
what does "rt" means at fopen line?

But, I want to to know to how to use sscanf functinality instead of strstr.

Please let me know how to extract the string with sscanf and then print it effectively. But thank you for your time. Hoping to get reply back from you.

You are confusing something called a "scanset" with what sscanf is doing in your example. A scanset is a CLASS of characters, for example, all lowercase:

Code:

/* sscanftest.c*/
int main()
{
	char	mystring[256];
	printf("Enter a string in lower case ");
	scanf("%[ a-z]",mystring); /* allow space character and all lc letters */
	printf("The string was ||%s||\n",mystring);
	return 0;
}

Here is what you get:
Notice:
1. the scanset does not look for a particular string like "model name"
scansets filter in (or out with ^ as the first character) desired characters.


2. it stops scanning when it hits a character not in the scanset - like the comma

In other words, sscanf does not do what you want it to do - look for a given string.
Your syntax should be "%[ <scanset goes here> ]".

Bottom line -- the strstr answer you already got works. scansets are not the
desired way to go here. HTH

Hello,

thank you so much for detaill answer. I cannot believe that we cannot use sscanf( ) here. But, thank you as I know a way now. But if I become able to extract the string with sscanf( ), I will definitely let you know by posting the method here.

Thank you.

't' - mode specifier
to open the file in text mode and not in binary mode

default is 't' when it is not specified with fopen

default value is set in _fmode in /usr/include/stdio.h

Thank you a lot. Just to let you know, as I am learning Ansi C now, I will be coming here with questions. I hope that it is okay. I know that there are lots of manuels, but I hope that I could get a website with manpage details and also with more practical coding examples.