$ cat fileSTARTUnixLinuxSTARTSolarisAixSCO 1. Join the lines following the pattern START without any delimiter.

$ awk '/START/{if (NR!=1)print "";next}{printf $0}END{print "";}' fileUnixLinuxSolarisAixSCO 2. Join the lines following the pattern START with space as delimiter.

$ awk '/START/{if (NR!=1)print "";next}{printf "%s ",$0}END{print "";}' fileUnix LinuxSolaris Aix SCO 3. Join the lines following the pattern START with comma as delimiter.

$ awk '/START/{if (x)print x;x="";next}{x=(!x)?$0:x","$0;}END{print x;}' fileUnix,LinuxSolaris,Aix,SCO 4. Join the lines following the pattern START with comma as delimiter with also the pattern matching line.

$ awk '/START/{if (x)print x;x="";}{x=(!x)?$0:x","$0;}END{print x;}' fileSTART,Unix,LinuxSTART,Solaris,Aix,SCO 5. Join the lines following the pattern START with comma as delimiter with also the pattern matching line. However, the pattern line should not be joined.

$ awk '/START/{if (x)print x;print;x="";next}{x=(!x)?$0:x","$0;}END{print x;}' fileSTARTUnix,LinuxSTARTSolaris,Aix,SCO 6. Other ways:

paste -d, -s file

cat file | xargs

 

REF:

http://www.theunixschool.com/2012/05/awk-join-or-merge-lines-on-finding.html

https://stackoverflow.com/questions/15758814/turning-multiple-lines-into-one-line-with-comma-separated-perl-sed-awk

 

==========================================================

AC  M07451

ID  V$PBX1_10

NA  PBX1

AC  M07452

ID  V$MEIS1_06

NA  Meis1

AC  M07453

ID  V$MEIS1BHOXA9PBX1A_01

NA  Meis1b:Hoxa9:Pbx1a

AC  M07454

ID  V$GLI1_Q3_01

NA  Gli1

AC  M07455

ID  V$GLI2_Q3

NA  Gli2

AC  M07456

ID  V$HOXA913_Q4

NA  HOX 9-13

awk '$0 ~ /^AC|^ID|^NA/'  conserved.new \

 |  awk '/AC  /{if (x)print x;x="";}{x=(!x)?$0:x","$0;}END{print x;}' \

    | sed 's/AC  //g' | sed 's/,ID  /\t/g' | sed 's/,NA  /\t/g' \

              >  genesymbol

M07451    V$PBX1_10    PBX1

M07452    V$MEIS1_06    Meis1

M07453    V$MEIS1BHOXA9PBX1A_01    Meis1b:Hoxa9:Pbx1a

M07454    V$GLI1_Q3_01    Gli1

M07455    V$GLI2_Q3    Gli2

==========================================================

 

more file

start111

aa

bb

cc

start222

dd

ee

awk '/start/{if (x)print x;x="";}{x=(!x)?$0:x","$0;}END{print x;}' file > bbb

more bbb

start111,aa,bb,cc

start222,dd,ee

awk -F"[|, ]" '{for(i=2;i<=NF;i++){print $1"|"$i}}' bbb

start111|aa

start111|bb

start111|cc

start222|dd

start222|ee