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     STYLE(6)                                                 STYLE(6)

     NAME
          style - Plan 9 coding conventions for C

     DESCRIPTION
          Plan 9 C code has its own conventions.  You would do well to
          follow them.  Here are a few:

          •  don't use `//' comments; some old Plan 9 code does, but
             we're converting it as we touch it.  We do sometimes use
             `//' to comment-out a few lines of code.

          •  avoid gotos.

          •  no tabs expanded to spaces.

          •  surround a binary operator (particular a low precedence
             one) with spaces; don't try to write the most compact
             code possible but rather the most readable.

          •  parenthesize expressions involving arithmetic and bit-
             wise operators; otherwise don't parenthesize heavily
             (e.g., as in Pascal).

          •  no white space before opening braces.

          •  no white space after the keywords `if', `for', `while',
             etc.

          •  no braces around single-line blocks (e.g., `if', `for',
             and `while' bodies).

          •  integer-valued functions return -1 on error, 0 or posi-
             tive on success.

          •  functions that return errors should set errstr(2).

          •  variable and function names are all lowercase, with no
             underscores.

          •  enum or #defined constants should be Uppercase (or UPPER-
             CASE).

          •  struct tags are Uppercase, with matching typedefs.

          •  automatic variables (local variables inside a function)
             are never initialized at declaration.

          •  follow the standard idioms: use `x < 0' not `0 > x', etc.

          •  don't write `!strcmp' (nor `!memcmp', etc.)  nor

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     STYLE(6)                                                 STYLE(6)

             `if(memcmp(a, b, c))'; always explicitly compare the
             result of string or memory comparison with zero using a
             relational operator.

          Ultimately, the goal is to write code that fits in with the
          other code around it and the system as a whole.  If the file
          you are editing already deviates from these guidelines, do
          what it does.  After you edit a file, a reader should not be
          able to tell just from coding style which parts you worked
          on.

        COMMENTS
          If your code is readable, you shouldn't need many comments.
          A line or two comment above a function explaining what it
          does is always welcome.

          Comment any code you find yourself wondering about for more
          than 2 seconds, even if it's to say that you don't under-
          stand what's going on.  Explain why.

          Don't use commenting as an excuse for writing confusing
          code.  Rewrite the code to make it clear.

        EFFICIENCY
          Do the simple thing.  Don't optimize unless you've measured
          the code and it is too slow.  Fix the data structures and
          the algorithms instead of going for little 5% tunings.

     SEE ALSO
          ``Notes on Programming in C'', Rob Pike,
          http://www.literateprogramming.com/pikestyle.pdf

     BUGS
          Some programs use very different styles, for example, rc.

          Some programs and programmers diverge from the above rules
          due to habits formed long before these rules.  Notably, some
          programs have a single space after a keyword and before an
          opening brace, and some initialize automatic variables at
          declaration.

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