1. Advanced File Processing
Chapter 10
Advanced File Processing

2. Objectives To discuss the formation and use of regular expressions
To explain file compression and how it can be performed
To explain the sorting process and how files can be sorted
To discuss searching for commands and files in the UNIX file structure
To describe searching files for expression, strings and patterns
To describe how database-type operations of cutting and pasting fields in a file can be performed
To discuss encoding and decoding of files
To explain file encryption and decryption
To cover the commands and primitives
> , ~, compress, crypt, .cut, egrep, fgrep, find, grep…
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3. Regular Expressions
Regular expressions allow you to specify a set of items by using a single character string, similar to the use of shell metacharacters
Commonly used tools that allow the use of regular expressions:
awk, ed, egrep, grep, sed and vi.
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4. Regular Expressions (Contd)
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5. Regular Expressions (Contd)
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6. Regular Expressions (Contd)
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7. Regular Expressions (Contd)
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8. Compressing Files The compress command Compress [options][file-list]
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9. Compressing Files (Contd)
The uncompress command
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10. Compressing Files (Contd)
The gzip command
gzip [options] [file-list]
The gunzip command
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11. Compressing Files (Contd)
The gexe command
gexe [options] [file-list]
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12. Compressing Files (Contd)
The zcat command
zcat [options] [file-list]
The pack and unpack commands
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13. Sorting Ordering a set of items according to some criteria
Systems in which sorting is used include:
Words in a dictionary
Names of people in a telephone directory and so on
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14. Sorting (Contd) UNIX sort utility sort [options] [file-list]
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15. Searching for Commands and Files
find
Whereis
which
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16. Searching Files grep [options] pattern [file-list]
egrep [options][string][file-list]
fgrep [options][expression][file-list]
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17. Cutting and Pasting cut –blist [-n][file-list] cut –clist [file-list]
cut –flist [-dchar][-s][file-list]
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18. Cutting and Pasting (Contd)
paste [options] file-list
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19. Encoding and Decoding uuencode [source-file] decode_label
uudecode [option] [encoded-file]
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20. File Encryption and Decryption
Encryption is a process by which a file is converted to a form completely different from its original version and that the transformed file in called encrypted file
The reverse process of transforming the file to its original form is known as decryption
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21. File Encryption and Decryption (Contd)
crypt [option]
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22. File Encryption and Decryption (Contd)
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23. File Encryption and Decryption (Contd)
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