Why UNIX?
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In the 1980s, UNIX became popular
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Customer demand for open systems:
 Application portability
 Vendor independence
 User portability
Time to market considerations
Major vendors (such as Sun, DEC, HP, IBM)
implemented UNIX based product lines.
Brief History
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UNIX
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Linux
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Created at Bell Labs, 1969
BSD during mid 70s
AT&T began offering System II in early 80s
defined in 1991
Red Hat, 1995
http://www.computerhope.com/history/unix.htm
UNIX Philosophy
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Simplicity
Reusability
Filters
Open Formats
Flexibility
What is the shell?
Utility program loaded when a user logs in
startup
init
getty
sh (bash)
login
Shell’s Responsibilities
interpreted
programming
languages
Program
Execution
variable and
filename
substitution
Shell
I/O
Redirection
environment
control
pipeline
hookup
Shell Substitutions
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Certain characters are interpreted by the
various Unix shells as “wildcards” for
filenames, also known as metacharacters
* - mathes 0 or more of any character
ls *.c
? - matches any single character
ls file0?.c
[...] - matches any single character if it is in
the list provided
ls file[0-9].c
Regular Expressions
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A formalized way to specify strings
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File names (shell commands)
Strings in text files (during editing)
Compilers (future topic)
Sed
Unfortunately, each use defines its own
special metacharacters
Regular Expressions
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LS – which files match A*[0-9]?.c
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AboutTime.c
AboutTime
A2.c
A2i.c
A211x.c
AllFilesGreaterThan12.c
A2char.c
Regular Expressions
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Write a regular expressions for:
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All files with an ‘X’ in the name
All files with an ‘X’ and a following ‘Y’
All file names with exactly 6 characters
All file names with more than 6 characters
All files that start with ‘a’ and end with ‘x’
All files names including an ‘a’ but fewer than
10 characters (this one is TOUGH!)
The Manual
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The man command
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man gcc
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Spacebar for next page and return for next
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line
q to quit
Also try info
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info gcc
grep Commands
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grep, egrep, fgrep
grep format:
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grep [options] search_string filename(s)
Options:
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-c
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-l
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-n
-v
Prints the count of matching lines rather than
the actual lines
prints the name of each file containing matching
lines, rather than the actual lines
precedes each line with a line number
inverse search, shows all lines that do not
match pattern
sort Command
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sort format:
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sort [options] filename
Options:
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-d
alphabetic, ignore punctuation
-f
ignore case for sorting
-r
reverse sort order
-o outfile output to file, not stdout
-n
arithmetic order
-tc
use ‘c’ to separate fields; default is
whitespace
find Command
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find format:
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find directory_name search_criteria action
Search Criteria:
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name filename
files that match filename
atime +-n files last accessed in days
mtime +-n files last modified in days
follow
follow symbolic links
find Command
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Actions:
-print
-exec cmd
-ok cmd
print the files found
execute command on files found
like exec, but prompts to execute
command first