Printing with sed or awk a line following a matching pattern

Question

Question  I d like to print a single line directly following a line that contains a matching pattern  My version of sed will not take the following syntax  it bombs out on  1p  which would seem like a simple solution  sed -n   ABC   1p  infile  I assume awk would be better to do multiline processing  but I am not sure how to do it

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Actually sed -n   pattern  n p   filename will fail if the pattern match continuous lines     seq 15  sed -n   1  n p   2 11 13 15   The expected answers should be   2 11 12 13 14 15   My solution is     sed -n -r  x     x p x  x  pattern  s       pattern s       h  filename   For example     seq 15  sed -n -r  x     x p x  x  1  s       1 s       h  2 11 12 13 14 15   Explains    x   at the beginning of each line from input  use x command to exchange the contents in pattern space  amp  hold space      x p x    if pattern space  which is the hold space actually  contains    this is just a indicator indicating if last line matched the pattern or not   then use x to exchange the actual content of current line to pattern space  use p to print current line  and x to recover this operation   x  recover the contents in pattern space and hold space   pattern  s       if current line does NOT match pattern  which means we should NOT print the NEXT following line  then use s      command to delete all contents in pattern space   pattern s        if current line matches pattern  which means we should print the NEXT following line  then we need to set a indicator to tell sed to print NEXT line  so use s       to substitute all contents in pattern space to a   the second command will use it to judge if last line matched the pattern or not   h  overwrite the hold space with the contents in pattern space  then  the content in hold space is      which means current line matches the pattern  or     which means current line does NOT match the pattern  the fifth step and sixth step can NOT exchange  because after s        the pattern space can NOT match  pattern   so the s      MUST be executed

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This might work for you  GNU sed    sed -n   a  regexp  n h p x ba   file   Use seds grep-like option -n and if the current line contains the required regexp replace the current line with the next  copy that line to the hold space  HS   print the line  swap the pattern space  PS  for the HS and repeat

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awk Version   awk   regexp    getline  print  0     filetosearch

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I needed to print ALL lines after the pattern   ok Ed  REGEX    so I settled on this one   sed -n   pattern   p    prints all lines after   and including   the pattern   But since I wanted to print all the lines AFTER   and exclude the pattern     sed -n   pattern   p    tail -n 2    all lines after first occurrence of pattern   I suppose in your case you can add a head -1 at the end  sed -n   pattern   p    tail -n 2   head -1   prints line after pattern

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Piping some greps can do it  it runs in POSIX shell and under BusyBox   cat my-file   grep -A1 my-regexp   grep -v --  --    grep -v my-regexp   -v will show non-matching lines -- is printed by grep to separate each match  so we skip that too

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If pattern match  copy next line into the pattern buffer  delete a return  then quit -- side effect is to print   sed   pattern    N  s    n    q    d

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It s the line after that match that you re interesting in  right  In sed  that could be accomplished like so   sed -n   ABC  n p   infile   Alternatively  grep s A option might be what you re looking for   -A NUM  Print NUM lines of trailing context after matching lines    For example  given the following input file   foo bar baz bash bongo   You could use the following     grep -A 1  bar  file bar baz   sed -n   bar  n p   file baz   Hope that helps

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Never use the word  pattern  as is it highly ambiguous  Always use  string  or  regexp   or in shell  globbing pattern    whichever it is you really mean   The specific answer you want is   awk  f print f 0   regexp  f 1   file   or specializing the more general solution of the Nth record after a regexp  idiom  c  below    awk  c amp  amp  --c   regexp  c 1   file   The following idioms describe how to select a range of records given a specific regexp to match   a  Print all records from some regexp   awk   regexp  f 1 f  file   b  Print all records after some regexp   awk  f  regexp  f 1   file   c  Print the Nth record after some regexp   awk  c amp  amp  --c  regexp  c N   file   d  Print every record except the Nth record after some regexp   awk  c amp  amp  --c next  regexp  c N 1  file   e  Print the N records after some regexp   awk  c amp  amp c--  regexp  c N   file   f  Print every record except the N records after some regexp   awk  c amp  amp c-- next  regexp  c N 1  file   g  Print the N records from some regexp   awk   regexp  c N c amp  amp c--  file   I changed the variable name from  f  for  found  to  c  for  count  where appropriate as that s more expressive of what the variable actually IS

[awk] Printing with sed or awk a line following a matching pattern

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