Want to check values are present or not in file [closed] - c

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Here I have one file which contains some information, and I want to check some values of tags are present or not in file.If present, then I want to retrieve these values.
Here number of tags is fixed and lenght of tag would not be more than 16 and length of value of tag is almost fix it would not more than 10 bytes.
From below file I want to check KERNEL tag value is present or not,FS tag value is present or not, etc etc.
I want to check all values are present or not after : (colon).
My file contains text like this.
KERNEL:2.31
FS:3.4
XLOADER:1.1
UBOOT:2.2
or like this
KERNEL:2.31
FS:
XLOADER:1.3
UBOOT:
I am using this code
#include <stdio.h>
int main() {
FILE *infile = fopen("example.txt", "r");
char buffer[256];
char value[128];
while (fgets(buffer, sizeof(buffer), infile))
if (1 == sscanf(buffer, "KERNEL:%s", value)) {
printf("Value = %s\n", value);
}
return 0;
}
but in code i have to call 4 this function 4 times for different different values. like KERNEL,FS, etc.
this code output like this
Value = 2.31
i read line from the data file and than i want to parse value of every tag (Means wants to identify values is present or not).
So this is Good way to do this thing can any body suggest me ?

Answer 1

Your question does not make it clear what context the file is in (or did not when I started answering). Presumably, it is a text file that the application can find by some means.
You've not specified whether the contents (tags) are supposed to be fixed, whether the file can contain other information, whether there's a comment convention in place, whether blank lines are allowed, what happens if a tag is missing altogether, what happens if there's an unexpected tag in the file, what happens if a tag is repeated (with the same version, with a different version). Are the tags case-sensitive; are leading blanks allowed before the tag; before the version; after the version? What characters are allowed in the version number? These are details that matter.
Let's assume that the list of names is fixed. Let's assume that tags are not longer than 7 (8 with terminal null). Let's assume that version numbers are not longer than 15 characters in total (16 allowing for terminal null). Let's assume that you need to keep a record of which tags you found and the version that you found.
In that case, you will end up with a data structure a bit like this:
typedef struct VersionInfo
{
char tag[8];
char version[16];
} VersionInfo;
static VersionInfo version_data[] =
{
{ "KERNEL", "" },
{ "FS", "" },
{ "XLOADER", "" },
{ "UBOOT", "" },
};
Clearly, with that basic structure available, you can write a function to read each line from the data file, discarding any comment or blank lines (if that's appropriate). You can probably use fgets() for this; the expected lines are short. You should probably complain about long lines, and decide whether to ignore them or stop processing. You can look for each of the tags in the version_data array, and when you find one, note whether it has been found before or not, and then find the version information on the line and copy it into the corresponding part of the version_data array.
You might extend the structure with an 'expected version' field as well as the actual version field. This will allow you to decide what to do based on the versions you find. You might have ranges related the allowable versions, based on what was known when the program was compiled, for example. You might allow the program that was compiled with 3.0.3 of something to run with 3.0.4 and later, and maybe you're even willing to work with 3.0.0 and later, but not any version 2.
Note that version comparison is a fine art in its own right. For example, the versions 3.0.3, 3.1.2, 3.6, 3.6.1, 3.6.1.2, and 3.10.0 should probably be treated as being in ascending order of version number. Using strcmp() won't achieve that (it will place 3.10.0 ahead of all the 3.6 versions).
I see that your example code uses sscanf() with a fixed string. That probably ties you to a fixed order and certainly not as flexible as the data structure allows you to be. If using sscanf(), I've be expecting to use a format such as:
if (sscanf(buffer, "%7s:%15s", tag, version) != 2)
...something up with the input line...
...process tag and version that you did find...
You can refine the scans with the character class notations:
if (sscanf(buffer, "%7[A-Z]:%15[0-9.]", tag, version) != 2)
This only accepts upper-case letters in the tag and only accepts digits and dots in the version information (but is quite happy with version "..0...0...0" which you probably shouldn't accept as valid).

Answer 2

Given your samples, the first approach I'd try is:
Read a line
Remove all whitespace
If the last character on the line is a colon <do something>
Else
Do something else