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The three most significant features of agrep that are not supported by
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the grep family are
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1) the ability to search for approximate patterns;
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for example, "agrep -2 homogenos foo" will find homogeneous as well
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as any other word that can be obtained from homogenos with at most
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2 substitutions, insertions, or deletions.
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"agrep -B homogenos foo" will generate a message of the form
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best match has 2 errors, there are 5 matches, output them? (y/n)
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for example, "agrep -2 homogenos foo" will find homogeneous as well
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as any other word that can be obtained from homogenos with at most
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2 substitutions, insertions, or deletions.
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"agrep -B homogenos foo" will generate a message of the form
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best match has 2 errors, there are 5 matches, output them? (y/n)
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2) agrep is record oriented rather than just line oriented; a record
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is by default a line, but it can be user defined;
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for example, "agrep -d '^From ' 'pizza' mbox"
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outputs all mail messages that contain the keyword "pizza".
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Another example: "agrep -d '$$' pattern foo" will output all
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paragraphs (separated by an empty line) that contain pattern.
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is by default a line, but it can be user defined;
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for example, "agrep -d '^From ' 'pizza' mbox"
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outputs all mail messages that contain the keyword "pizza".
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Another example: "agrep -d '$$' pattern foo" will output all
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paragraphs (separated by an empty line) that contain pattern.
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3) multiple patterns with AND (or OR) logic queries.
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For example, "agrep -d '^From ' 'burger,pizza' mbox"
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outputs all mail messages containing at least one of the
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two keywords (, stands for OR).
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"agrep -d '^From ' 'good;pizza' mbox" outputs all mail messages
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containing both keywords.
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For example, "agrep -d '^From ' 'burger,pizza' mbox"
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outputs all mail messages containing at least one of the
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two keywords (, stands for OR).
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"agrep -d '^From ' 'good;pizza' mbox" outputs all mail messages
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containing both keywords.
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Putting these options together one can ask queries like
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7. fix a bug regarding exit status.
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-------------------------------------------------------------------------------
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REVISIONS TO AGREP, FALL '93
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8. Options can now be specified in a single group of characters after one '-'.
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9. Made agrep callable as a library routine from a separate function. The
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interface is: memagrep(argc, argv, searchbufferlen, searchbuffer),
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the pattern to be searched for and the options being specified EXACTLY as
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if they are being specified on the command line. The only difference is
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that instead of the file-names to look at, the user should specify a buffer
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and its length. Sample user programs are in ../user directory.
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In memagrep(), there are TWO peculiarities:
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1. Peculiarity #1 -- at the end of the buffer, the user must have N bytes
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of valid virtual memory, where N is the length of the pattern to be
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searched. This space is used by agrep to speed up the checking of the
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termination condition. Its contents are restored before memagrep()
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returns -- however, some space must be there... else you'll get SIGSEGV.
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I might trap segv and do a longjmp, but that'll be in a new version!
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2. The search buffer must begin with a newline so that it is easy for
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agrep to output matched lines. This also avoids some copying.
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Ofcourse, if we copied the user's search buffer into another buffer which
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meets both the above conditions, memagrep() will no longer be fast -- and
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speed is the primary goal.
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10. Added some filter-programs to make agrep search thru compressed files.
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Also added some features in the Makefile which allows the user to build
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an agrep with a dummyfilter so that agrep remains independent of tcompress.
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The definitions needed in agrep to interface with tcompress are in defs.h
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11. Added a library interface for searching thru a specified set of files,
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fileagrep(), which is similar to memagrep(). This is used by glimpse.
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Had to modify some other things and fix some bugs (see CHANGES).
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- Dec 1993 (coding), Jan 1993 (debugging).
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-------------------------------------------------------------------------------
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CODING NOTE: sgrep.c and newmgrep.c use a similar while(fill_buf) loop
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with start and end, while others use loops with an internal variable i.
added
removed
README
