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\par\pard\qc\li0\tx0\tx20000{\b\fs34 A\~Tour\~of\~the\~ast\~Commands\~and\~Libraries}{\b\fs30\line
Glenn\~Fowler\line
\line
AT&T\~Labs\~-\~Research\line
\line
Murray\~Hill,\~NJ\~07974\line
\line
}\line
\par\pard\fi-560\li840\tx840\tx20000{\brdrt\brdrsh\par}{\b\fs32#{\footnote HTML2RTF.1Introduction} 1\~\~Introduction} \par\pard\li840\tx840\tx20000 The {\i ast
}commands and libraries were developed by the Software Engineering Research
Department ({\i aka }the Advanced Software [Technology] Department) at
AT&T Bell Laboratories, Murray Hill, NJ. The strength of {\i ast }is
how its individual components combine to form a cohesive computing environment
across UNIX\'ae and non-UNIX platforms. {\uldb FN577}{\v HTML2RTF.FN577}{\*\comment Cohesiveness*}\~[\~Footnote
test. \~]\~is maintained by well-defined library interfaces for algorithms
upon which the commands are built. In many cases a library implementation
was the driving force behind command implementations. \par\pard\fi-560\li840\tx840\tx20000{\brdrt\brdrsh\par}{\b\fs32#{\footnote HTML2RTF.2Motivation} 2\~\~Motivation}
\par\pard\li840\tx840\tx20000 Why should you consider using the {\i ast }software? After all, many
of the commands look like what's already in {\f1 /bin }and {\f1 /usr/local/gnu/bin}.
Although there is some replication, there are also some commands you won't
find anywhere else: {\i the }ksh93, nmake, the 3d filesystem, cia, and
yeast. \par\pard\fi-560\li840\tx840\tx20000{\brdrt\brdrsh\par}{\b\fs32#{\footnote HTML2RTF.3Installation} 3\~\~Installation}
\par\pard\li840\tx840\tx20000 The {\i ast }software installs in a single directory hierarchy, rooted
at {\f1 $INSTALLROOT}, usually {\f1 /usr/local/ast }or {\f1 /usr/add-on/ast}.
The top level {\f1 $INSTALLROOT }directories are: \line
{\f1\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~bin\~\~\~\~\~\~executable\~binaries\~and\~scripts\~\line
\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~fun\~\~\~\~\~\~}{\i ksh93}{\f1\~shell\~functions\~\~\~\line
\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~lib\~\~\~\~\~\~libraries\~\~\~\~\~\~\~\line
\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~lib/}{\i command}{\f1\~\~\~\~\~\~related\~files\~for\~}{\i command}{\f1\~\~\~\~\~\~\~\line
\~\~\~\~\~\~\~\~\~\~\~\~\~\~\~src/cmd/}{\i xxx}{\f1\~\~\~\~\~\~source\~for\~command\~}{\i xxx}{\f1\~\~\line
\~\~\~\~\~\~\~\~\~\~\~\~src/lib/lib}{\i xxx}{\f1\~\~\~\~\~\~source\~for\~library\~}{\i xxx}{\f1\~\~\line
}To
access the commands and related data files: \line
{\f1\~\~\~\~\~\~\~\~export\~PATH=$INSTALLROOT/bin:$PATH\~\~\~\~\~\~\line
}For
each {\i command }that has a related data file {\i file}, {\i file }is
found by searching {\f1 $PATH }for e.g., the magic file for the file command
is {\f1 ../lib/file/magic }on {\f1 $PATH}. If {\f1 $HOME/bin }is before
{\f1 $INSTALLROOT/bin }in {\f1 $PATH }then you can selectively override
standard {\i ast }related files by placing them in the directory This allows
executables to be built without hard-coded pathnames and also requires only
a change in {\f1 $PATH }when {\f1 $INSTALLROOT }changes. On systems with
shared libraries one of \line
{\f1\~\~\~\~\~\~\~\~export\~LD_LIBRARY_PATH=$INSTALLROOT/lib:$LD_LIBRARY_PATH\~\~\~\~\~\~\~\~\line
\~\~\~\~\~\~\~\~export\~LIBPATH=$INSTALLROOT/lib:$LIBPATH\~\~\~\~\~\~\~\~\line
\~\~\~\~\~\~\~\~export\~LPATH=$INSTALLROOT/lib:$LPATH\~\~\~\~\line
}is
required to locate the {\i ast }shared libraries. \par\pard\li840\tx840\tx20000\par\pard\fi-560\li840\tx840\tx20000{\brdrt\brdrsh\par}{\b\fs32#{\footnote HTML2RTF.4Exploration} 4\~\~Exploration}
\par\pard\li840\tx840\tx20000{\i tw }combines {\i find }and {\i xargs}. It provides C style expressions
on path names and elements of {\f1 struct stat}. To find suspicious executables:
\line
{\f1\~\~\~\~\~\~\~\~tw\~-d\~/\~-e\~"uid=='root'\~&&\~(mode&'u+s')\~&&\~parent.uid!=uid"\~\~\~\~\~\line
}to
change the owner of all of bozo's files: \line
{\f1\~\~\~\~\~\~\~\~tw\~-d\~/\~-e\~"uid=='bozo'"\~chown\~clown:circus\~\~\~\~\~\line
}{\i tw
}collects file pathname arguments up to the exec arg limit before it executes
the command. For paranoid users: \line
{\f1\~\~\~\~\~\~\~\~tw\~chmod\~go-rwx\~\line
}which
is equivalent to: \line
{\f1\~\~\~\~\~\~\~\~chmod\~-R\~go-rwx\~\line
}(Now
you don't need to add a {\f1 -R }option to your favorite commands.) To find
all source files that include {\f1 foo.h}: \line
{\f1\~\~\~\~\~\~\~\~tw\~-e\~"name=='*.[chly]'"\~grep\~-l\~'^#.*include.*["<]foo.h[>"]'\~\~\~\line
}{\i libast
}handles the magic number matching for the {\i file }command. The magic
file, {\f1 $INSTALLROOT/lib/file/magic}, is carefully constructed to give
the same output across all architectures: \line
{\f1\~\~\~\~\~\~\~\~cd\~$HOME/arch\~\~\~\line
\~\~\~\~\~\~\~\~file\~*/bin/cat\~\~\line
}might
produce: \line
{\f1\~\~\~\~\~\~\~\~att.i386/bin/cat:\~\~\~elf\~i386\~executable,\~32-bit,\~little-endian,\~..\~\~\~\~\~\~\line
\~\~\~\~\~\~\~\~bsd.i386/bin/cat:\~\~\~bsd\~386\~executable,\~compact,\~paged,\~pure,\~no..\~\~\~\~\~\~\line
\~\~\~\~\~\~\~\~hp.pa/bin/cat:\~\~\~\~\~\~hp\~pa-risc\~executable,\~shared,\~dynamically\~l..\~\~\~\~\~\~\line
\~\~\~\~\~\~\~\~sgi.mips2/bin/cat:\~\~elf\~mips\~executable,\~32-bit,\~dynamically\~lin..\~\~\~\~\~\~\line
\~\~\~\~\~\~\~\~sol.sun4/bin/cat:\~\~\~elf\~sparc\~executable,\~32-bit,\~dynamically\~li..\~\~\~\~\~\~\line
\~\~\~\~\~\~\~\~sun4/bin/cat:\~\~\~\~\~\~\~sun\~sparc\~executable,\~paged,\~dynamically\~lin..\~\~\~\~\~\~\line
}{\i tw
}uses the same interface, making it easy to search for files based on
type, name and content. The following searches for executable scripts: \line
{\f1\~\~\~\~\~\~\~\~tw\~-e\~"(mode&'+x')\~&&\~type!=DIR\~&&\~magic!='*executable*'"\~\~\~\~\~\~\~\line
}The
{\i tw }algorithm efficiently detects file system loops, so following symbolic
links is not a problem. The same algorithm is used by all {\i ast }commands
that traverse directory hierarchies, and the following options to control
pathname resolution: {\f1\~\~\~\~\~\~\~\~-L\~(logical)\~\~\~\~\~\~\~\~\~follow\~symbolic\~links\~\~\~\~\~\~\line
\~\~\~\~\~\~\~\~-P\~(physical)\~\~\~\~\~\~\~\~don't\~follow\~symbolic\~links\~\~\~\~\~\~\~\~\line
\~\~\~\~\~\~\~\~-H\~(metaphysical)\~\~\~\~-L\~for\~command\~line\~files,\~-P\~otherwise\~\~\~\~\line
}The
{\i ksh93 }{\i getconf }builtin controls the default traversal mode: \line
{\f1\~\~\~\~\~\~\~\~getconf\~PATH_RESOLVE\~-\~\{\~logical,\~physical,\~metaphysical\~\}\~\~\~\~\~\~\line
}
\par\pard\fi-560\li840\tx840\tx20000{\brdrt\brdrsh\par}{\b\fs32#{\footnote HTML2RTF.5Configuration} 5\~\~Configuration} \par\pard\li840\tx840\tx20000\par\pard\fi-560\li840\tx840\tx20000{\brdrt\brdrsh\par}{\b\fs32#{\footnote HTML2RTF.6Compression} 6\~\~Compression}
\par\pard\li840\tx840\tx20000\par\pard\fi-560\li840\tx840\tx20000{\brdrt\brdrsh\par}{\b\fs32#{\footnote HTML2RTF.7Conclusion} 7\~\~Conclusion} \par\pard\li840\tx840\tx20000{\brdrt\brdrsh\par}\par\pard\li0\tx0\tx20000 April 18,
1997
}
