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Category:TXR: Difference between revisions
Complex example.
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TXR is a new text extraction language implemented in [[C]], running on [[Linux]] (and possibly other [[POSIX]] platforms).
==Simple Query==
Here is a very basic hello-world-type TXR query that re-implements the "free" utility:
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means, "Next, please switch to scanning the output of this echo command with some variables substituted in. Then capture entire first line of this command into the USED variable."
== Complex Query ==
Here is a TXR query for computing the complete dependencies of a C source file (including system and compiler headers) on a typical GNU/Linux system, demonstrating features like parallel clauses, recursion and exception handling.
<lang txr>@(define process_file (dir file already_visited visited_out))
@ (local this_file next_file header_dir next_dir next_dir2 visited_out_next)
@ (bind this_file `@dir@file`)
@ (none)
@ (bind already_visited this_file)
@ (end)
@ (merge already_visited already_visited this_file)
@ (next this_file)
@ (collect)
@ (cases)
#include "@*header_dir/@next_file"
@ (bind next_dir `@dir@header_dir/`)
@ (or)
#include "@next_file"
@ (bind next_dir dir)
@ (or)
#@/ */include <@next_file>
@ (bind next_dir sys_includes)
@ (bind next_dir2 gcc_includes)
@ (or)
#@/ */include <@*header_dir/@next_file>
@ (bind next_dir `@sys_includes@header_dir/`)
@ (bind next_dir2 `@gcc_includes@header_dir/`)
@ (or)
#@/ */include_next <@next_file>
@ (bind next_dir gcc_includes)
@ (or)
#@/ */include_next <@*header_dir/@next_file>
@ (bind next_dir `@gcc_includes@header_dir/`)
@ (end)
@ (try)
@ (process_file next_dir next_file already_visited visited_out_next)
@ (merge already_visited already_visited visited_out_next)
@ (catch)
@ (try)
@ (process_file next_dir2 next_file already_visited visited_out_next)
@ (merge already_visited already_visited visited_out_next)
@ (catch)
@ (end)
@ (end)
@ (end)
@ (bind visited_out this_file)
@ (try)
@ (flatten visited_out_next)
@ (merge visited_out visited_out visited_out_next)
@ (catch)
@ (end)
@(end)
@(next :args)
@(cases)
@*dir/@*file.@suffix
@ (bind directory `@dir/`)
@(or)
@*file.@suffix
@ (bind directory "")
@(end)
@(next `!gcc -print-search-dirs`)
install: @gcc_install
@(bind gcc_includes `@{gcc_install}include/`)
@(bind sys_includes "/usr/include/")
@(process_file directory `@file.@suffix` nil list_out)
@(output)
@(rep) @list_out@(first)@file.o:@(end)
@(end)</lang>
Sample run:
<pre>$ txr dep.txr match.c
match.o: /usr/include/stdio.h /usr/include/features.h /usr/include/sys/cdefs.h /usr/include/bits/wordsize.h /usr/include/gnu/stubs.h /usr/include/gnu/stubs-32.h /usr/lib/gcc/i586-redhat-linux/4.4.1/include/stddef.h /usr/include/bits/types.h /usr/include/libio.h /usr/include/_G_config.h /usr/include/wchar.h /usr/lib/gcc/i586-redhat-linux/4.4.1/include/stdarg.h /usr/include/bits/wchar.h /usr/include/wctype.h /usr/include/endian.h /usr/include/bits/endian.h /usr/include/bits/byteswap.h /usr/include/xlocale.h /usr/include/bits/wchar2.h /usr/include/bits/wchar-ldbl.h /usr/include/gconv.h /usr/include/bits/stdio-lock.h /usr/include/bits/libc-lock.h /usr/include/pthread.h /usr/include/sched.h /usr/include/time.h /usr/include/bits/time.h /usr/include/bits/sched.h /usr/include/signal.h /usr/include/bits/signum.h /usr/include/bits/siginfo.h /usr/include/bits/sigaction.h /usr/include/bits/sigcontext.h /usr/include/asm/sigcontext.h /usr/include/linux/types.h /usr/include/linux/posix_types.h /usr/include/linux/stddef.h /usr/include/asm/posix_types.h /usr/include/asm/types.h /usr/include/asm-generic/int-ll64.h /usr/include/bits/sigstack.h /usr/include/sys/ucontext.h /usr/include/bits/pthreadtypes.h /usr/include/bits/sigthread.h /usr/include/bits/setjmp.h /usr/include/bits/libio-ldbl.h /usr/include/bits/stdio_lim.h /usr/include/bits/sys_errlist.h /usr/include/getopt.h /usr/include/ctype.h /usr/include/bits/stdio.h /usr/include/bits/stdio2.h /usr/include/bits/stdio-ldbl.h /usr/include/stdlib.h /usr/include/bits/waitflags.h /usr/include/bits/waitstatus.h /usr/include/alloca.h /usr/include/bits/stdlib.h /usr/include/bits/stdlib-ldbl.h /usr/include/string.h /usr/include/bits/string.h /usr/include/bits/string2.h /usr/include/bits/string3.h /usr/include/assert.h /usr/include/errno.h /usr/include/bits/errno.h /usr/include/linux/errno.h /usr/include/asm/errno.h /usr/include/asm-generic/errno.h /usr/include/asm-generic/errno-base.h /usr/include/dirent.h /usr/include/bits/dirent.h /usr/include/bits/posix1_lim.h /usr/include/bits/local_lim.h /usr/include/linux/limits.h /usr/include/setjmp.h config.h lib.h gc.h unwind.h regex.h /usr/include/limits.h /usr/lib/gcc/i586-redhat-linux/4.4.1/include/limits.h /usr/lib/gcc/i586-redhat-linux/4.4.1/include/syslimits.h /usr/include/bits/posix2_lim.h /usr/include/bits/xopen_lim.h stream.h parser.h txr.h utf8.h filter.h match.h</pre>
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