# print first 10 lines of file (emulates behavior of "head")
sed 10q

# print the last 10 lines of a file (emulates "tail")
sed -e :a -e '$q;N;11,$D;ba'

# print the last 2 lines of a file (emulates "tail -2")
sed '$!N;$!D'

# print the last line of a file (emulates "tail -1")
sed '$!d'                    # method 1
sed -n '$p'                  # method 2

# print only lines which match regular expression (emulates "grep")
sed -n '/regexp/p'           # method 1
sed '/regexp/!d'             # method 2

# print only lines which do NOT match regexp (emulates "grep -v")
sed -n '/regexp/!p'          # method 1, corresponds to above
sed '/regexp/d'              # method 2, simpler syntax

# reverse order of lines (emulates "tac")
# bug/feature in HHsed v1.5 causes blank lines to be deleted
sed '1!G;h;$!d'               # method 1
sed -n '1!G;h;$p'             # method 2

# reverse each character on the line (emulates "rev")
sed '/\n/!G;s/\(.\)\(.*\n\)/&\2\1/;//D;s/.//'

# join pairs of lines side-by-side (like "paste")
sed '$!N;s/\n/ /'

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# print the line immediately before a regexp, but not the line
# containing the regexp
sed -n '/regexp/{g;1!p;};h'

# print the line immediately after a regexp, but not the line
# containing the regexp
sed -n '/regexp/{n;p;}'

# print 1 line of context before and after regexp, with line number
# indicating where the regexp occurred (similar to "grep -A1 -B1")
sed -n -e '/regexp/{=;x;1!p;g;$!N;p;D;}' -e h

# grep for AAA and BBB and CCC (in any order)
sed '/AAA/!d; /BBB/!d; /CCC/!d'

# grep for AAA and BBB and CCC (in that order)
sed '/AAA.*BBB.*CCC/!d'

# grep for AAA or BBB or CCC (emulates "egrep")
sed -e '/AAA/b' -e '/BBB/b' -e '/CCC/b' -e d    # most seds
gsed '/AAA\|BBB\|CCC/!d'                        # GNU sed only

# print paragraph if it contains AAA (blank lines separate paragraphs)
# HHsed v1.5 must insert a 'G;' after 'x;' in the next 3 scripts below
sed -e '/./{H;$!d;}' -e 'x;/AAA/!d;'

# print paragraph if it contains AAA and BBB and CCC (in any order)
sed -e '/./{H;$!d;}' -e 'x;/AAA/!d;/BBB/!d;/CCC/!d'

# print paragraph if it contains AAA or BBB or CCC
sed -e '/./{H;$!d;}' -e 'x;/AAA/b' -e '/BBB/b' -e '/CCC/b' -e d
gsed '/./{H;$!d;};x;/AAA\|BBB\|CCC/b;d'         # GNU sed only

# print only lines of 65 characters or longer
sed -n '/^.\{65\}/p'

# print only lines of less than 65 characters
sed -n '/^.\{65\}/!p'        # method 1, corresponds to above
sed '/^.\{65\}/d'            # method 2, simpler syntax

# print section of file from regular expression to end of file
sed -n '/regexp/,$p'

# print section of file based on line numbers (lines 8-12, inclusive)
sed -n '8,12p'               # method 1
sed '8,12!d'                 # method 2

# print line number 52
sed -n '52p'                 # method 1
sed '52!d'                   # method 2
sed '52q;d'                  # method 3, efficient on large files

# beginning at line 3, print every 7th line
gsed -n '3~7p'               # GNU sed only
sed -n '3,${p;n;n;n;n;n;n;}' # other seds

# print section of file between two regular expressions (inclusive)
sed -n '/Iowa/,/Montana/p'             # case sensitive

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# print all of file EXCEPT section between 2 regular expressions
sed '/Iowa/,/Montana/d'

# delete duplicate, consecutive lines from a file (emulates "uniq").
# First line in a set of duplicate lines is kept, rest are deleted.
sed '$!N; /^\(.*\)\n\1$/!P; D'

# delete duplicate, nonconsecutive lines from a file. Beware not to
# overflow the buffer size of the hold space, or else use GNU sed.
sed -n 'G; s/\n/&&/; /^\([ -~]*\n\).*\n\1/d; s/\n//; h; P'

# delete all lines except duplicate lines (emulates "uniq -d").
sed '$!N; s/^\(.*\)\n\1$/\1/; t; D'

# delete the first 10 lines of a file
sed '1,10d'

# delete the last line of a file
sed '$d'

# delete the last 2 lines of a file
sed 'N;$!P;$!D;$d'

# delete the last 10 lines of a file
sed -e :a -e '$d;N;2,10ba' -e 'P;D'   # method 1
sed -n -e :a -e '1,10!{P;N;D;};N;ba'  # method 2

# delete every 8th line
gsed '0~8d'                           # GNU sed only
sed 'n;n;n;n;n;n;n;d;'                # other seds

# delete ALL blank lines from a file (same as "grep '.' ")
sed '/^$/d'                           # method 1
sed '/./!d'                           # method 2

# delete all CONSECUTIVE blank lines from file except the first; also
# deletes all blank lines from top and end of file (emulates "cat -s")
sed '/./,/^$/!d'          # method 1, allows 0 blanks at top, 1 at EOF
sed '/^$/N;/\n$/D'        # method 2, allows 1 blank at top, 0 at EOF

# delete all CONSECUTIVE blank lines from file except the first 2:
sed '/^$/N;/\n$/N;//D'

# delete all leading blank lines at top of file
sed '/./,$!d'

# delete all trailing blank lines at end of file
sed -e :a -e '/^\n*$/{$d;N;ba' -e '}'  # works on all seds
sed -e :a -e '/^\n*$/N;/\n$/ba'        # ditto, except for gsed 3.02*

# delete the last line of each paragraph
sed -n '/^$/{p;h;};/./{x;/./p;}'

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# IN UNIX ENVIRONMENT: convert DOS newlines (CR/LF) to Unix format
sed 's/.$//'               # assumes that all lines end with CR/LF
sed 's/^M$//'              # in bash/tcsh, press Ctrl-V then Ctrl-M
sed 's/\x0D$//'            # gsed 3.02.80, but top script is easier

# IN UNIX ENVIRONMENT: convert Unix newlines (LF) to DOS format
sed "s/$/`echo -e \\\r`/"            # command line under ksh
sed 's/$'"/`echo \\\r`/"             # command line under bash
sed "s/$/`echo \\\r`/"               # command line under zsh
sed 's/$/\r/'                        # gsed 3.02.80

# IN DOS ENVIRONMENT: convert Unix newlines (LF) to DOS format
sed "s/$//"                          # method 1
sed -n p                             # method 2

# IN DOS ENVIRONMENT: convert DOS newlines (CR/LF) to Unix format
# Can only be done with UnxUtils sed, version 4.0.7 or higher.
# Cannot be done with other DOS versions of sed. Use "tr" instead.
sed "s/\r//" infile >outfile         # UnxUtils sed v4.0.7 or higher
tr -d \r <infile >outfile            # GNU tr version 1.22 or higher

# delete leading whitespace (spaces, tabs) from front of each line
# aligns all text flush left
sed 's/^[ \t]*//'                    # see note on '\t' at end of file

# delete trailing whitespace (spaces, tabs) from end of each line
sed 's/[ \t]*$//'                    # see note on '\t' at end of file

# delete BOTH leading and trailing whitespace from each line
sed 's/^[ \t]*//;s/[ \t]*$//'

# insert 5 blank spaces at beginning of each line (make page offset)
sed 's/^/     /'

# align all text flush right on a 79-column width
sed -e :a -e 's/^.\{1,78\}$/ &/;ta'  # set at 78 plus 1 space

# center all text in the middle of 79-column width. In method 1,
# spaces at the beginning of the line are significant, and trailing
# spaces are appended at the end of the line. In method 2, spaces at
# the beginning of the line are discarded in centering the line, and
# no trailing spaces appear at the end of lines.
sed  -e :a -e 's/^.\{1,77\}$/ & /;ta'                     # method 1
sed  -e :a -e 's/^.\{1,77\}$/ &/;ta' -e 's/\( *\)\1/\1/'  # method 2

# if a line ends with a backslash, append the next line to it
sed -e :a -e '/\\$/N; s/\\\n//; ta'

# if a line begins with an equal sign, append it to the previous line
# and replace the "=" with a single space
sed -e :a -e '$!N;s/\n=/ /;ta' -e 'P;D'

# add commas to numeric strings, changing "1234567" to "1,234,567"
gsed ':a;s/\B[0-9]\{3\}\>/,&/;ta'                     # GNU sed
sed -e :a -e 's/\(.*[0-9]\)\([0-9]\{3\}\)/\1,\2/;ta'  # other seds

# add commas to numbers with decimal points and minus signs (GNU sed)
gsed ':a;s/\(^\|[^0-9.]\)\([0-9]\+\)\([0-9]\{3\}\)/\1\2,\3/g;ta'

# add a blank line every 5 lines (after lines 5, 10, 15, 20, etc.)
gsed '0~5G'                  # GNU sed only
sed 'n;n;n;n;G;'             # other seds

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# double space a file
sed G

# double space a file which already has blank lines in it. Output file
# should contain no more than one blank line between lines of text.
sed '/^$/d;G'

# triple space a file
sed 'G;G'

# undo double-spacing (assumes even-numbered lines are always blank)
sed 'n;d'

# insert a blank line above every line which matches "regex"
sed '/regex/{x;p;x;}'

# insert a blank line below every line which matches "regex"
sed '/regex/G'

# insert a blank line above and below every line which matches "regex"
sed '/regex/{x;p;x;G;}'

# number each line of a file (simple left alignment). Using a tab (see
# note on '\t' at end of file) instead of space will preserve margins.
sed = filename | sed 'N;s/\n/\t/'

# number each line of a file (number on left, right-aligned)
sed = filename | sed 'N; s/^/     /; s/ *\(.\{6,\}\)\n/\1  /'

# number each line of file, but only print numbers if line is not blank
sed '/./=' filename | sed '/./N; s/\n/ /'

# count lines (emulates "wc -l")
sed -n '$='

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'no interpolation'
"#{interpolation}, and backslashes\n"
%q(no interpolation)
%Q(interpolation and backslashes)
%(interpolation and backslashes)
`echo command interpretation with interpolation and backslashes`
%x(echo command interpretation with interpolation and backslashes)

# Backslashes
\t (tab), \n (newline), \r (carriage return), \f (form feed),
\b (backspace), \a (bell), \e (escape), \s (whitespace), \nnn (octal),
\xnn (hexadecimal), \cx (control x), \C-x (control x), \M-x (meta x),
\M-\C-x (meta control x)

# Here Docs
<<identifier   - interpolated, goes until identifier
<<"identifier" - same thing
<<'identifier' - no interpolation
<<-identifier  - you can indent the identifier by using "-" in front

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File.join(p1, p2, ... pN)           => "p1/p2/.../pN" platform independent paths
File.new(path, modestring="r")      => file
File.new(path, modenum [, permnum]) => file
IO.readlines(path)                  => array
File.open(fileName, aModeString="r") {|file| block}
File.open(fileName [, aModeNum [, aPermNum ]]) {|file| block}
IO.foreach(path, sepstring=$/) {|line| block}

# Mode Strings
r   # Read-only, starts at beginning of file (default mode).
r+  # Read-write, starts at beginning of file.
w   # Write-only, truncates existing file to zero length or creates a new file for writing.
w+  # Read-write, truncates existing file to zero length or creates a new file for reading and writing.
a   # Write-only, starts at end of file if file exists, otherwise creates a new file for writing.
a+  # Read-write, starts at end of file if file exists, otherwise creates a new file for reading and writing.
b   # (DOS/Windows only) Binary file mode (may appear with any of the key letters listed above).

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# Variables
$global_variable
@@class_variable
@instance_variable
[OtherClass::]CONSTANT
local_variable

# Pseudo variables
self     the receiver of the current method
nil      the sole instance of the Class NilClass(represents false)
true     the sole instance of the Class TrueClass(typical true value)
false    the sole instance of the Class FalseClass(represents false)
__FILE__ the current source file name.
__LINE__ the current line number in the source file.
__END__  the end of the ruby file, ignore everything after

# Pre-defined variables
$!         The exception information message set by 'raise'.
$@         Array of backtrace of the last exception thrown.
$&         The string matched by the last successful pattern match in this scope.
$`         The string to the left  of the last successful match.
$'         The string to the right of the last successful match.
$+         The last bracket matched by the last successful match.
$1         The Nth group of the last successful match. May be > 1.
$~         The information about the last match in the current scope.
$=         The flag for case insensitive, nil by default.
$/         The input record separator, newline by default.
$\         The output record separator for the print and IO#write. Default is nil.
$,         The output field separator for the print and Array#join.
$;         The default separator for String#split.
$.         The current input line number of the last file that was read.
$<         The virtual concatenation file of the files given on command line.
$>         The default output for print, printf. $stdout by default.
$_         The last input line of string by gets or readline.
$0         Contains the name of the script being executed. May be assignable.
$*         Command line arguments given for the script sans args.
$$         The process number of the Ruby running this script.
$?         The status of the last executed child process.
$:         Load path for scripts and binary modules by load or require.
$"         The array contains the module names loaded by require.
$DEBUG     The status of the -d switch.
$FILENAME  Current input file from $<. Same as $<.filename.
$LOAD_PATH The alias to the $:.
$stderr    The current standard error output.
$stdin     The current standard input.
$stdout    The current standard output.
$VERBOSE   The verbose flag, which is set by the -v switch.
$-0        The alias to $/.
$-a        True if option -a is set. Read-only variable.
$-d        The alias to $DEBUG.
$-F        The alias to $;.
$-i        In in-place-edit mode, this variable holds the extension, otherwise nil.
$-I        The alias to $:.
$-l        True if option -l is set. Read-only variable.
$-p        True if option -p is set. Read-only variable.
$-v        The alias to $VERBOSE.
$-w        True if option -w is set.

# Pre-defined global constants
TRUE              The typical true value.
FALSE             The false itself.
NIL               The nil itself.
STDIN             The standard input. The default value for $stdin.
STDOUT            The standard output. The default value for $stdout.
STDERR            The standard error output. The default value for $stderr.
ENV               The hash contains current environment variables.
ARGF              The alias to the $<.
ARGV              The alias to the $*.
DATA              The file object of the script, pointing just after __END__.
RUBY_VERSION      The ruby version string (VERSION was deprecated).
RUBY_RELEASE_DATE The release date string.
RUBY_PLATFORM     The platform identifier.

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