A) The UNIX shell interprets a number of characters in special ways. These characters are most often used with UNIX commands - as arguments and for other means. The following list contains most of UNIX's special characters.
NEWLINE - initiates command execution
; - separates commands on same line
( ) - groups commands or identifies a function
& - executes a command in the background
| - pipe
> - redirects standard output
>> - appends standard output
< - redirects standard input * - wildcard for any number of characters in a file name ? - wildcard for a single character in a file name \ - quotes the following character ' - quotes a string preventing all substitutions " - quotes a string allowing variable and command substitution ` - performs command substitution [ ] - denotes a character class in a file name $ - references a variable { } - command grouping within a function . - executes a command (if at beginning of line) # - begins a comment : - null command B) Examples
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1. Use the * character in file names to match any number of characters. The following command:
ls *.txt
Will match the following files:
chapter1.txt doc.txt memo.txt a.txt
Will not match the following files:
doctxt txt.memo
2. Use the ? character in file names to match any single character. The following command:
ls ???.txt
Will match the following files:
one.txt doc.txt two.txt
Will not match the following files:
chap1.txt doctxt
3. Use the [ ] characters in file names to match any character within a range of characters. The following command:
ls chapter[1-3].txt
Will match the following files:
chapter1.txt chapter2.txt chapter3.txt
Will not match the following files:
chap1.txt chapter4.txt
If you want to know the details about these special characters then have a look at,
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