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xstr(1) General Commands Manual xstr(1) NAME xstr - Extracts strings from C programs to implement shared strings SYNOPSIS xstr [-c] [file|-] The xstr command maintains a file called strings into which strings in component parts of a large program are hashed. OPTIONS Extracts strings from the specified file. DESCRIPTION The strings extracted by xstr are replaced with references to this ar- ray. This serves to implement shared constant strings, most useful if they are also read-only. The following command extracts the strings from the C source in file, replacing string references by expressions of the form (&xstr[number]) for some number. xstr -c file The xstr command uses file as input; the resulting C text is placed in the file x.c to then be compiled. The strings from this file are ap- pended to the strings file if they are not there already. Repeated strings and strings that are suffixes of existing strings do not cause changes to the file. If a string is a suffix of another string in the file, but the shorter string is seen first by xstr, both strings are placed in the file strings. After all components of a large program are compiled, a file xs.c de- claring the common xstr space can be created by a command of the fol- lowing form: xstr Compile and load this xs.c file with the rest of the program. Some C compilers may, by default, put strings in a read-only text section. The xstr command can also be used on a single file. The following com- mand creates files x.c and xs.c as before, without using or affecting a strings file in the same directory. xstr file It may be useful to run xstr after the C preprocessor if any macro def- initions yield strings or if there is conditional code that contains strings that may not be needed. The xstr command reads from its stan- dard input when the argument - (dash) is given. An appropriate command sequence for running xstr after the C preprocessor is as follows: cc -E file.c | xstr -c - cc -c x.c mv x.o file.o The xstr command does not touch the file strings unless new items are added, thus make can avoid remaking xs.o unless truly necessary. EXAMPLES To extract the strings from the C source in the file.c parameter, re- placing string references by expressions of the form (&xstr[number]), enter: xstr -c file An appropriate declaration of the xstr array is prepended to file. The resulting C text is placed in the file x.c, to then be compiled. To declare the common xstr array space in the xs.c file, enter: xstr FILES File that contains the extracted strings. Modified C source. C source for definition of array xstr. Temporary file when the xstr command does not touch strings. SEE ALSO Commands: mkstr(1) xstr(1)