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copied table 3.1 from unix programming environment book

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tomit4 2022-05-01 14:08:46 -07:00
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Taken from the Unix Programming Environment by Brian Kernighan and Rob Pike (pg. 76):
____________________ Table 3.1: Shell Metacharacters ___________________
> prog >file direct standard output to file
>> prog >>file append standard output to file
< prog <file take a standard input from file
| p1|p2 connect standard output of p1 to standard intput of p2
<<str here document: standard input follows, up to next str on a line by itself
* match any string of zero or more characters in filenames
? match any single character in filenames
[ccc] match any single character from ccc in filenames; ranges like 0-9 or a-z are legal
; command terminator: p1;p2 does p1, then p2
& like ; but doesn't wait for p1 to finish
` run command(s) in ...; output replaces `...`
(...) run command(s) in ... in a sub-shell
{...} run command(s) in ... in current shell (rarely used)
$1, $2, etc. $0...$9 replaced by arguments to shell file
$var value of shell variable var
${var} value of var; avoids confusion when concatenated with text; (see also Table 5.3)
\ \c take character c literally, \newline discarded
'...' take ... literally
"..." take ... literally after $, `...` and \ interpreted
# if # starts word, rest of line is a comment (not in 7th Ed.)
var=value assign to variable var
p1 && p2 run p1; if successful, run p2
p1 || p2 run p1; if unsuccessful, run p2