Difference between angle bracket and double quotes while including header files in C

Question

Possible Duplicate    What is the difference between  include  lt filename gt  and  include    filename           What is the difference between angle bracket  lt   gt  and double quotes     while including header files in C     I mean which files are supposed to be included using eg   include  lt QPushButton gt  and which files are to be included using eg   include  MyFile h

User · Accepted Answer

It s compiler dependent    That said  in general using   prioritizes headers in the current working directory over system headers    lt  gt  usually is used for system headers   From to the specification  Section 6 10 2       A preprocessing directive of the form      include  lt h-char-sequence gt  new-line       searches a sequence of implementation-defined places for a header identified uniquely by the specified sequence between the  lt  and  gt  delimiters  and causes the replacement of that directive by the entire contents of the header  How the places are specified or the header identified is implementation-defined       A preprocessing directive of the form      include  q-char-sequence  new-line       causes the replacement of that directive by the entire contents of the source file identified by the specified sequence between the   delimiters  The named source file is searched for in an implementation-defined manner  If this search is not supported  or if the search fails  the directive is reprocessed as if it read      include  lt h-char-sequence gt  new-line       with the identical contained sequence  including  gt  characters  if any  from the original   directive        So on most compilers  using the    first checks your local directory  and if it doesn t find a match then moves on to check the system paths   Using  lt  gt  starts the search with system headers

User · Answer

When you use angle brackets  the compiler searches for the file in the include path list  When you use double quotes  it first searches the current directory  i e  the directory where the module being compiled is  and only then it ll search the include path list   So  by convention  you use the angle brackets for standard includes and the double quotes for everything else  This ensures that in the  not recommended  case in which you have a local header with the same name as a standard header  the right one will be chosen in each case

[c++] Difference between angle bracket < > and double quotes " " while including header files in C++?

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