# Where should I put the bib-file to use it directly in \bibliography{bibfile}?

I've usually referred as \bibliography{path_to_bib_file/bibfile} to find the bib-file of my Bibliography.

Where should I put my bib-file in order to simply use the command \bibliography{bibfile} ?

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Just save it at the same folder as your .tex file. –  Sigur Jun 21 '13 at 17:21
On GNU/Linux (and related) with TeX Live: ~/texmf/bibtex/bib –  jon Jun 21 '13 at 17:45
I've already answered this question in your previous question: see here –  karlkoeller Jun 21 '13 at 18:00
As this is already covered in an answer to a previous question by @karlkoeller, I'm minded to close this as a dupe. –  Joseph Wright Jun 21 '13 at 18:51
@jon, not always we have that folder. I'm using TeXlive 2011 and I don't have it. –  Sigur Jun 21 '13 at 20:08

This is actually distribution-dependent. karlkoeller's answer covers the MikTeX case. For TeXLive it is a little bit different. Here, bibtex will search the paths given in the environment variable BIBINPUTS for .bib files, and the paths in BSTINPUTS for bibliography style files (.bst). In case you don't provide a BIBINPUTS variable, BibTex will use a system default that is defined in texmf.cnf. (You can find texmf.cnf via kpsewhich texmf.cnf)
BIBINPUTS = .;$TEXMF/bibtex/bib//  there, which means that the current directory (. is the short-hand for that) is searched first, then the directories under $TEXMF/bibtex/bib. $TEXMF is your system's TEXMF tree, i.e., the place where TeXLive has been installed. In contrast to MikTeX's bibtex, in TeXLive we don't have a --include-directory command line switch, which is a pity. So many people will put their .bib files in the same directory as their .tex files, and BibTeX will find them without any further configuration. As I reuse my bibliography databases quite often, I collect them in a central place (${HOME}/bib usually) and set BIBINPUTS accordingly in .bashrc.