Agrep is a tool for fast text searching allowing errors.

The three most significant features of agrep that are not supported by
the grep family are
1) the ability to search for approximate patterns;
    for example, "agrep -2 homogenos foo" will find homogeneous as well
    as any other word that can be obtained from homogenos with at most
    2 substitutions, insertions, or deletions.
    "agrep -B homogenos foo" will generate a message of the form
    best match has 2 errors, there are 5 matches, output them? (y/n)
2) agrep is record oriented rather than just line oriented;  a record
    is by default a line, but it can be user defined;
    for example, "agrep -d '^From ' 'pizza' mbox"
    outputs all mail messages that contain the keyword "pizza".
    Another example:  "agrep -d '$$' pattern foo" will output all
    paragraphs (separated by an empty line) that contain pattern.
3) multiple patterns with AND (or OR) logic queries.
    For example, "agrep -d '^From ' 'burger,pizza' mbox"
    outputs all mail messages containing at least one of the
    two keywords (, stands for OR).
    "agrep -d '^From ' 'good;pizza' mbox" outputs all mail messages
    containing both keywords.

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