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前面已经研究了 SED1LINE. 下面贴出 AWK1LINE 作个对照， 看看
sed 与 awk 如何处理同一个问题。
- HANDY ONE-LINERS FOR AWK 22 July 2003
- compiled by Eric Pement <pemente@northpark.edu> version 0.22
-
- USAGE:
- Unix: awk '/pattern/ {print "$1"}' # standard Unix shells
- DOS/Win: awk '/pattern/ {print "$1"}' # okay for DJGPP compiled
- awk "/pattern/ {print \"$1\"}" # required for Mingw32
- Most of my experience comes from version of GNU awk (gawk) compiled for
- Win32. Note in particular that DJGPP compilations permit the awk script
- to follow Unix quoting syntax '/like/ {"this"}'. However, the user must
- know that single quotes under DOS/Windows do not protect the redirection
- arrows (<, >) nor do they protect pipes (|). Both are special symbols
- for the DOS/CMD command shell and their special meaning is ignored only
- if they are placed within "double quotes." Likewise, DOS/Win users must
- remember that the percent sign (%) is used to mark DOS/Win environment
- variables, so it must be doubled (%%) to yield a single percent sign
- visible to awk.
- If I am sure that a script will NOT need to be quoted in Unix, DOS, or
- CMD, then I normally omit the quote marks. If an example is peculiar to
- GNU awk, the command 'gawk' will be used. Please notify me if you find
- errors or new commands to add to this list (total length under 65
- characters). I usually try to put the shortest script first.
- FILE SPACING:
- # double space a file
- awk '1;{print ""}'
- awk 'BEGIN{ORS="\n\n"};1'
- # 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.
- # NOTE: On Unix systems, DOS lines which have only CRLF (\r\n) are
- # often treated as non-blank, and thus 'NF' alone will return TRUE.
- awk 'NF{print $0 "\n"}'
- # triple space a file
- awk '1;{print "\n"}'
- NUMBERING AND CALCULATIONS:
- # precede each line by its line number FOR THAT FILE (left alignment).
- # Using a tab (\t) instead of space will preserve margins.
- awk '{print FNR "\t" $0}' files*
- # precede each line by its line number FOR ALL FILES TOGETHER, with tab.
- awk '{print NR "\t" $0}' files*
- # number each line of a file (number on left, right-aligned)
- # Double the percent signs if typing from the DOS command prompt.
- awk '{printf("%5d : %s\n", NR,$0)}'
- # number each line of file, but only print numbers if line is not blank
- # Remember caveats about Unix treatment of \r (mentioned above)
- awk 'NF{$0=++a " :" $0};{print}'
- awk '{print (NF? ++a " :" :"") $0}'
- # count lines (emulates "wc -l")
- awk 'END{print NR}'
- # print the sums of the fields of every line
- awk '{s=0; for (i=1; i<=NF; i++) s=s+$i; print s}'
- # add all fields in all lines and print the sum
- awk '{for (i=1; i<=NF; i++) s=s+$i}; END{print s}'
- # print every line after replacing each field with its absolute value
- awk '{for (i=1; i<=NF; i++) if ($i < 0) $i = -$i; print }'
- awk '{for (i=1; i<=NF; i++) $i = ($i < 0) ? -$i : $i; print }'
- # print the total number of fields ("words") in all lines
- awk '{ total = total + NF }; END {print total}' file
- # print the total number of lines that contain "Beth"
- awk '/Beth/{n++}; END {print n+0}' file
- # print the largest first field and the line that contains it
- # Intended for finding the longest string in field #1
- awk '$1 > max {max=$1; maxline=$0}; END{ print max, maxline}'
- # print the number of fields in each line, followed by the line
- awk '{ print NF ":" $0 } '
- # print the last field of each line
- awk '{ print $NF }'
- # print the last field of the last line
- awk '{ field = $NF }; END{ print field }'
- # print every line with more than 4 fields
- awk 'NF > 4'
- # print every line where the value of the last field is > 4
- awk '$NF > 4'
- TEXT CONVERSION AND SUBSTITUTION:
- # IN UNIX ENVIRONMENT: convert DOS newlines (CR/LF) to Unix format
- awk '{sub(/\r$/,"");print}' # assumes EACH line ends with Ctrl-M
- # IN UNIX ENVIRONMENT: convert Unix newlines (LF) to DOS format
- awk '{sub(/$/,"\r");print}
- # IN DOS ENVIRONMENT: convert Unix newlines (LF) to DOS format
- awk 1
- # IN DOS ENVIRONMENT: convert DOS newlines (CR/LF) to Unix format
- # Cannot be done with DOS versions of awk, other than gawk:
- gawk -v BINMODE="w" '1' infile >outfile
- # Use "tr" instead.
- 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
- awk '{sub(/^[ \t]+/, ""); print}'
- # delete trailing whitespace (spaces, tabs) from end of each line
- awk '{sub(/[ \t]+$/, "");print}'
- # delete BOTH leading and trailing whitespace from each line
- awk '{gsub(/^[ \t]+|[ \t]+$/,"");print}'
- awk '{$1=$1;print}' # also removes extra space between fields
- # insert 5 blank spaces at beginning of each line (make page offset)
- awk '{sub(/^/, " ");print}'
- # align all text flush right on a 79-column width
- awk '{printf "%79s\n", $0}' file*
- # center all text on a 79-character width
- awk '{l=length();s=int((79-l)/2); printf "%"(s+l)"s\n",$0}' file*
- # substitute (find and replace) "foo" with "bar" on each line
- awk '{sub(/foo/,"bar");print}' # replaces only 1st instance
- gawk '{$0=gensub(/foo/,"bar",4);print}' # replaces only 4th instance
- awk '{gsub(/foo/,"bar");print}' # replaces ALL instances in a line
- # substitute "foo" with "bar" ONLY for lines which contain "baz"
- awk '/baz/{gsub(/foo/, "bar")};{print}'
- # substitute "foo" with "bar" EXCEPT for lines which contain "baz"
- awk '!/baz/{gsub(/foo/, "bar")};{print}'
- # change "scarlet" or "ruby" or "puce" to "red"
- awk '{gsub(/scarlet|ruby|puce/, "red"); print}'
- # reverse order of lines (emulates "tac")
- awk '{a[i++]=$0} END {for (j=i-1; j>=0;) print a[j--] }' file*
- # if a line ends with a backslash, append the next line to it
- # (fails if there are multiple lines ending with backslash...)
- awk '/\\$/ {sub(/\\$/,""); getline t; print $0 t; next}; 1' file*
- # print and sort the login names of all users
- awk -F ":" '{ print $1 | "sort" }' /etc/passwd
- # print the first 2 fields, in opposite order, of every line
- awk '{print $2, $1}' file
- # switch the first 2 fields of every line
- awk '{temp = $1; $1 = $2; $2 = temp}' file
- # print every line, deleting the second field of that line
- awk '{ $2 = ""; print }'
- # print in reverse order the fields of every line
- awk '{for (i=NF; i>0; i--) printf("%s ",i);printf ("\n")}' file
- # remove duplicate, consecutive lines (emulates "uniq")
- awk 'a !~ $0; {a=$0}'
- # remove duplicate, nonconsecutive lines
- awk '! a[$0]++' # most concise script
- awk '!($0 in a) {a[$0];print}' # most efficient script
- # concatenate every 5 lines of input, using a comma separator
- # between fields
- awk 'ORS=%NR%5?",":"\n"' file
- SELECTIVE PRINTING OF CERTAIN LINES:
- # print first 10 lines of file (emulates behavior of "head")
- awk 'NR < 11'
- # print first line of file (emulates "head -1")
- awk 'NR>1{exit};1'
- # print the last 2 lines of a file (emulates "tail -2")
- awk '{y=x "\n" $0; x=$0};END{print y}'
- # print the last line of a file (emulates "tail -1")
- awk 'END{print}'
- # print only lines which match regular expression (emulates "grep")
- awk '/regex/'
- # print only lines which do NOT match regex (emulates "grep -v")
- awk '!/regex/'
- # print the line immediately before a regex, but not the line
- # containing the regex
- awk '/regex/{print x};{x=$0}'
- awk '/regex/{print (x=="" ? "match on line 1" : x)};{x=$0}'
- # print the line immediately after a regex, but not the line
- # containing the regex
- awk '/regex/{getline;print}'
- # grep for AAA and BBB and CCC (in any order)
- awk '/AAA/; /BBB/; /CCC/'
- # grep for AAA and BBB and CCC (in that order)
- awk '/AAA.*BBB.*CCC/'
- # print only lines of 65 characters or longer
- awk 'length > 64'
- # print only lines of less than 65 characters
- awk 'length < 64'
- # print section of file from regular expression to end of file
- awk '/regex/,0'
- awk '/regex/,EOF'
- # print section of file based on line numbers (lines 8-12, inclusive)
- awk 'NR==8,NR==12'
- # print line number 52
- awk 'NR==52'
- awk 'NR==52 {print;exit}' # more efficient on large files
- # print section of file between two regular expressions (inclusive)
- awk '/Iowa/,/Montana/' # case sensitive
- SELECTIVE DELETION OF CERTAIN LINES:
- # delete ALL blank lines from a file (same as "grep '.' ")
- awk NF
- awk '/./'
- CREDITS AND THANKS:
- Special thanks to Peter S. Tillier for helping me with the first release
- of this FAQ file.
- For additional syntax instructions, including the way to apply editing
- commands from a disk file instead of the command line, consult:
- "sed & awk, 2nd Edition," by Dale Dougherty and Arnold Robbins
- O'Reilly, 1997
- "UNIX Text Processing," by Dale Dougherty and Tim O'Reilly
- Hayden Books, 1987
- "Effective awk Programming, 3rd Edition." by Arnold Robbins
- O'Reilly, 2001
- To fully exploit the power of awk, one must understand "regular
- expressions." For detailed discussion of regular expressions, see
- "Mastering Regular Expressions, 2d edition" by Jeffrey Friedl
- (O'Reilly, 2002).
- The manual ("man") pages on Unix systems may be helpful (try "man awk",
- "man nawk", "man regexp", or the section on regular expressions in "man
- ed"), but man pages are notoriously difficult. They are not written to
- teach awk use or regexps to first-time users, but as a reference text
- for those already acquainted with these tools.
- USE OF '\t' IN awk SCRIPTS: For clarity in documentation, we have used
- the expression '\t' to indicate a tab character (0x09) in the scripts.
- All versions of awk, even the UNIX System 7 version should recognize
- the '\t' abbreviation.
- #---end of file---
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发表于 2005-01-07 11:27
