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Sed

Submitted by xman on Sun, 17/09/2006 - 12:21pm
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Generic command format:

[address]command

command = d, a, i, c, r, w, q, ... d: Delete. a: Append. i: Insert. c: Change. r: Read. w: Write. q: Quit.

Group command format:

address{
command1
command2
command3
}

Substitution format:

[address]s/pattern/replacement/flags

flags = n, g, p, or w file. n: A number n represents nth occurrence. g: Global. p: Print. w file: Write to file.

Transform format:

[address]y/abc/xyz/

Translate a->x, b->y, and c->z.

[address] can be lines found by regular expression matches, range of lines.

s/abc/xyz/p Replace abc by xyz, and print (required 'p' if we use "sed -n" to suppress printing all lines).
s/abc/pqr/
s/pqr/xyz/		 Replace abc by pqr, then replace pqr by xyz. Effectively, abc and pqr becomes xyz.
/abc/s/pqr/xyz/g Find lines with abc, then replace pqr in the line by xyz. 'g' -> Replaces all pqr in the line.
1d Deletes the first line.
$d Deletes the last line.
/^$/d Deletes blank lines.
3,10d Deletes line 3 to line 10 inclusive.
3,10!d Deletes all lines except line 3 to line 10 inclusive.
10,$d Deletes line 10 to last line inclusive.
\(abc\)\+ Match one or more abc. Regular expression needs '\'.
abc+ Match literal abc+.
# A comment Comment.
s!abc!xyz! Replace abc by xyz, but using ! as delimiter.
a\abc Append abc to the matching line.
i\abc Insert abc before the matching line.
c\abc Change the matching line to abc.
= Print line with line number.
n Output the contents of the pattern space and read next line.
r file Read file.
w file Write file.
& Represent the regular expression matching string (used in replacement string).
\3 Match 3th substring in the regular expression using \( \).
s/\(a\)\(b\)/\2\1/ Replace ab by ba.
s/abc/xyz/2 Replace the 2nd abc by xyz.

There are other commands like multi-line commands (N, D, P), copying/appending pattern space to hold space vice versa (h,H,g,G,x), label(:labelname), branch to label (b), conditional branch (t).

Reference: UNIX Power Tools: sed & awk by Dale Dougherty