What is the easiest way to parse an INI File in C++?

I'm trying to parse an INI file using C++. Any tips on what is the best way to achieve this? Should I use the Windows API tools for INI file processing (with which I am totally unfamiliar), an open-source solution or attempt to parse it manually?

If you need a cross-platform solution, try Boost's Program Options library.

You can use the Windows API functions, such as GetPrivateProfileString() and GetPrivateProfileInt().

I have never parsed ini files, so I can't be too specific on this issue.
But i have one advice:
Don't reinvent the wheel as long as an existing one meets your requirements

<http://en.wikipedia.org/wiki/INI_file#Accessing_INI_files>
<http://sdl-cfg.sourceforge.net/>
<http://sourceforge.net/projects/libini/>
<http://www.codeproject.com/KB/files/config-file-parser.aspx>

Good luck :)

If you are already using Qt

QSettings my_settings("filename.ini", QSettings::IniFormat);

Then read a value

my_settings.value("GroupName/ValueName", <<DEFAULT_VAL>>).toInt()

There are a bunch of other converter that convert your INI values into both standard types and Qt types. See Qt documentation on QSettings for more information.

I use SimpleIni. It's cross-platform.

this question is a bit old, but I will post my answer. I have tested various INI classes (you can see them on my website) and I also use simpleIni because I want to work with INI files on both windows and winCE. Window's GetPrivateProfileString() works only with the registry on winCE.

It is very easy to read with simpleIni. Here is an example:

#include "SimpleIni\SimpleIni.h"    
CSimpleIniA ini;
ini.SetUnicode();
ini.LoadFile(FileName);
const char * pVal = ini.GetValue(section, entry, DefaultStr);

inih is a simple ini parser written in C, it comes with a C++ wrapper too. Example usage:

#include "INIReader.h"    

INIReader reader("test.ini");

std::cout << "version="
          << reader.GetInteger("protocol", "version", -1) << ", name="
          << reader.Get("user", "name", "UNKNOWN") << ", active="
          << reader.GetBoolean("user", "active", true) << "\n";

The author has also a list of existing libraries here.

Have you tried http://www.hyperrealm.com/libconfig/">libconfig</a>;; very JSON-like syntax. I prefer it over XML configuration files.

If you are interested in platform portability, you can also try Boost.PropertyTree. It supports ini as persistancy format, though the property tree my be 1 level deep only.

Unless you plan on making the app cross-platform, using the Windows API calls would be the best way to go. Just ignore the note in the API documentation about being provided only for 16-bit app compatibility.

I know this question is very old, but I came upon it because I needed something cross platform for linux, win32... I wrote the function below, it is a single function that can parse INI files, hopefully others will find it useful.

rules & caveats: buf to parse must be a NULL terminated string. Load your ini file into a char array string and call this function to parse it. section names must have [] brackets around them, such as this [MySection], also values and sections must begin on a line without leading spaces. It will parse files with Windows \r\n or with Linux \n line endings. Comments should use # or // and begin at the top of the file, no comments should be mixed with INI entry data. Quotes and ticks are trimmed from both ends of the return string. Spaces are only trimmed if they are outside of the quote. Strings are not required to have quotes, and whitespaces are trimmed if quotes are missing. You can also extract numbers or other data, for example if you have a float just perform a atof(ret) on the ret buffer.

//  -----note: no escape is nessesary for inner quotes or ticks-----
//  -----------------------------example----------------------------
//  [Entry2]
//  Alignment   = 1
//  LightLvl=128
//  Library     = 5555
//  StrValA =  Inner "quoted" or 'quoted' strings are ok to use
//  StrValB =  "This a "quoted" or 'quoted' String Value"
//  StrValC =  'This a "tick" or 'tick' String Value'
//  StrValD =  "Missing quote at end will still work
//  StrValE =  This is another "quote" example
//  StrValF =  "  Spaces inside the quote are preserved "
//  StrValG =  This works too and spaces are trimmed away
//  StrValH =
//  ----------------------------------------------------------------
//12oClocker super lean and mean INI file parser (with section support)
//set section to 0 to disable section support
//returns TRUE if we were able to extract a string into ret value
//NextSection is a char* pointer, will be set to zero if no next section is found
//will be set to pointer of next section if it was found.
//use it like this... char* NextSection = 0;  GrabIniValue(X,X,X,X,X,&NextSection);
//buf is data to parse, ret is the user supplied return buffer
BOOL GrabIniValue(char* buf, const char* section, const char* valname, char* ret, int retbuflen, char** NextSection)
{
	if(!buf){*ret=0; return FALSE;}

    char* s = buf; //search starts at "s" pointer
    char* e = 0;   //end of section pointer

    //find section
    if(section)
    {
		int L = strlen(section);
		SearchAgain1:
		s = strstr(s,section); if(!s){*ret=0; return FALSE;}    //find section
		if(s > buf && (*(s-1))!='\n'){s+=L; goto SearchAgain1;} //section must be at begining of a line!
		s+=L;                                                   //found section, skip past section name
		while(*s!='\n'){s++;} s++;                              //spin until next line, s is now begining of section data
		e = strstr(s,"\n[");                                    //find begining of next section or end of file
		if(e){*e=0;}                                            //if we found begining of next section, null the \n so we don't search past section
		if(NextSection)                                         //user passed in a NextSection pointer
		{ if(e){*NextSection=(e+1);}else{*NextSection=0;} }     //set pointer to next section
	}

	//restore char at end of section, ret=empty_string, return FALSE
	#define RESTORE_E     if(e){*e='\n';}
	#define SAFE_RETURN   RESTORE_E;  (*ret)=0;  return FALSE

	//find valname
	int L = strlen(valname);
	SearchAgain2:
	s = strstr(s,valname); if(!s){SAFE_RETURN;}             //find valname
	if(s > buf && (*(s-1))!='\n'){s+=L; goto SearchAgain2;} //valname must be at begining of a line!
	s+=L;                                                   //found valname match, skip past it
	while(*s==' ' || *s == '\t'){s++;}                      //skip spaces and tabs
	if(!(*s)){SAFE_RETURN;}                                 //if NULL encounted do safe return
	if(*s != '='){goto SearchAgain2;}                       //no equal sign found after valname, search again
	s++;                                                    //skip past the equal sign
	while(*s==' '  || *s=='\t'){s++;}                       //skip spaces and tabs
	while(*s=='\"' || *s=='\''){s++;}                       //skip past quotes and ticks
	if(!(*s)){SAFE_RETURN;}                                 //if NULL encounted do safe return
	char* E = s;                                            //s is now the begining of the valname data
	while(*E!='\r' && *E!='\n' && *E!=0){E++;} E--;         //find end of line or end of string, then backup 1 char
	while(E > s && (*E==' ' || *E=='\t')){E--;}             //move backwards past spaces and tabs
	while(E > s && (*E=='\"' || *E=='\'')){E--;}            //move backwards past quotes and ticks
	L = E-s+1;                                              //length of string to extract NOT including NULL
	if(L<1 || L+1 > retbuflen){SAFE_RETURN;}                //empty string or buffer size too small
	strncpy(ret,s,L);                                       //copy the string
	ret[L]=0;                                               //null last char on return buffer
	RESTORE_E;
	return TRUE;

	#undef RESTORE_E
	#undef SAFE_RETURN
}

How to use... example....

char sFileData[] = "[MySection]\r\n"
"MyValue1 = 123\r\n"
"MyValue2 = 456\r\n"
"MyValue3 = 789\r\n"
"\r\n"
"[MySection]\r\n"
"MyValue1 = Hello1\r\n"
"MyValue2 = Hello2\r\n"
"MyValue3 = Hello3\r\n"
"\r\n";
char str[256];
char* sSec = sFileData;
char secName[] = "[MySection]"; //we support sections with same name
while(sSec)//while we have a valid sNextSec
{
	//print values of the sections
	char* next=0;//in case we dont have any sucessful grabs
	if(GrabIniValue(sSec,secName,"MyValue1",str,sizeof(str),&next)) { printf("MyValue1 = [%s]\n",str); }
	if(GrabIniValue(sSec,secName,"MyValue2",str,sizeof(str),0))     { printf("MyValue2 = [%s]\n",str); }
	if(GrabIniValue(sSec,secName,"MyValue3",str,sizeof(str),0))     { printf("MyValue3 = [%s]\n",str); }
	printf("\n");
	sSec = next; //parse next section, next will be null if no more sections to parse
}

I ended up using inipp which is not mentioned in this thread.

https://github.com/mcmtroffaes/inipp

Was a MIT licensed header only implementation which was simple enough to add to a project and 4 lines to use.

Maybe a late answer..But, worth knowing options..If you need a cross-platform solution , definitely you can try GLIB,, its interesting.. (https://developer.gnome.org/glib/stable/glib-Key-value-file-parser.html)