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XSTR(1)             UNIX Programmer's Manual              XSTR(1)



N\bNA\bAM\bME\bE
    xstr - extract strings from C programs to implement shared
    strings

S\bSY\bYN\bNO\bOP\bPS\bSI\bIS\bS
    x\bxs\bst\btr\br [ -\b-c\bc ] [ -\b- ] [ file ]

D\bDE\bES\bSC\bCR\bRI\bIP\bPT\bTI\bIO\bON\bN
    _\bX_\bs_\bt_\br maintains a file _\bs_\bt_\br_\bi_\bn_\bg_\bs into which strings in com-
    ponent parts of a large program are hashed.  These strings
    are replaced with references to this common area.  This
    serves to implement shared constant strings, most useful if
    they are also read-only.

    The command

         x\bxs\bst\btr\br -\b-c\bc name

    will extract the strings from the C source in name, replac-
    ing string references by expressions of the form
    (&xstr[number]) for some number.  An appropriate declaration
    of _\bx_\bs_\bt_\br is prepended to the file.  The resulting C text is
    placed in the file _\bx._\bc, to then be compiled.  The strings
    from this file are placed in the _\bs_\bt_\br_\bi_\bn_\bg_\bs data base if they
    are not there already.  Repeated strings and strings which
    are suffices of existing strings do not cause changes to the
    data base.

    After all components of a large program have been compiled a
    file _\bx_\bs._\bc declaring the common _\bx_\bs_\bt_\br space can be created by
    a command of the form

         x\bxs\bst\btr\br

    This _\bx_\bs._\bc file should then be compiled and loaded with the
    rest of the program.  If possible, the array can be made
    read-only (shared) saving space and swap overhead.

    _\bX_\bs_\bt_\br can also be used on a single file.  A command

         x\bxs\bst\btr\br name

    creates files _\bx._\bc and _\bx_\bs._\bc as before, without using or
    affecting any _\bs_\bt_\br_\bi_\bn_\bg_\bs file in the same directory.

    It may be useful to run _\bx_\bs_\bt_\br after the C preprocessor if any
    macro definitions yield strings or if there is conditional
    code which contains strings which may not, in fact, be
    needed.  _\bX_\bs_\bt_\br reads from its standard input when the argu-
    ment `-' is given.  An appropriate command sequence for run-
    ning _\bx_\bs_\bt_\br after the C preprocessor is:




Printed 7/9/88             May 7, 1986                          1






XSTR(1)             UNIX Programmer's Manual              XSTR(1)



         c\bcc\bc -\b-E\bE name.c | x\bxs\bst\btr\br -\b-c\bc -
         c\bcc\bc -\b-c\bc x.c
         m\bmv\bv x.o name.o

    _\bX_\bs_\bt_\br does not touch the file _\bs_\bt_\br_\bi_\bn_\bg_\bs unless new items are
    added, thus _\bm_\ba_\bk_\be can avoid remaking _\bx_\bs._\bo unless truly neces-
    sary.

F\bFI\bIL\bLE\bES\bS
    strings        Data base of strings
    x.c       Massaged C source
    xs.c      C source for definition of array `xstr'
    /tmp/xs*  Temp file when `xstr name' doesn't touch _\bs_\bt_\br_\bi_\bn_\bg_\bs

S\bSE\bEE\bE A\bAL\bLS\bSO\bO
    mkstr(1)

B\bBU\bUG\bGS\bS
    If a string is a suffix of another string in the data base,
    but the shorter string is seen first by _\bx_\bs_\bt_\br both strings
    will be placed in the data base, when just placing the
    longer one there will do.

































Printed 7/9/88             May 7, 1986                          2