How to merge every two lines into one from the command line

Question

I have a text file with the following format  The first line is the  KEY  and the second line is the  VALUE     KEY 4048 1736 string 3 KEY 0 1772 string 1 KEY 4192 1349 string 1 KEY 7329 2407 string 2 KEY 0 1774 string 1   I need the value in the same line as of the key  So the output should look like this     KEY 4048 1736 string 3 KEY 0 1772 string 1 KEY 4192 1349 string 1 KEY 7329 2407 string 2 KEY 0 1774 string 1   It will be better if I could use some delimiter like   or     KEY 4048 1736 string   3   How do I merge two lines into one

User · Answer

nawk   0    string    printf   s    0  getline  printf   s n    0   filename   This reads as   0    string       matches any lines that end with the word string printf             so print the first line without newline getline            get the next line printf   s n       print the whole line and carriage return

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Although it seems the previous solutions would work  if a single anomaly occurs in the document the output would go to pieces  Below is a bit safer   sed -n   KEY   N s  n   p    somefile txt

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In the case where I needed to combine two lines  for easier processing   but allow the data past the specific  I found this to be useful  data txt  string1 x string2 y string3 string4     cat data txt   nawk   0    string1     printf   s     0  getline  printf   s n    0  getline     print     gt  converted data txt   output then looks like   converted data txt  string1 x string2 y string3 string4

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Another solutions using vim  just for reference    Solution 1    Open file in vim vim filename  then execute command    normal Jj   This command is very easy to understand         for all the lines    normal   execute normal command  Jj   execute Join command  then jump to below line   After that  save the file and exit with  wq  Solution 2    Execute the command in shell  vim -c     normal Jj  filename  then save the file and exit with  wq

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awk   awk  NR 2 printf   s    0 next  1  yourFile   note  there is an empty line at the end of output   sed   sed  N s  n     yourFile

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You can use xargs like this   xargs -a file

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Another approach using vim would be    g KEY join   This applies a join  to the line below it  to all lines that have the word KEY in it  Result   KEY 4048 1736 string 3 KEY 0 1772 string 1 KEY 4192 1349 string 1 KEY 7329 2407 string 2 KEY 0 1774 string 1

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Here is my solution in bash   while read line1  do read line2  echo   line1   line2   done  lt  data txt

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Alternative to sed  awk  grep   xargs -n2 -d  n    This is best when you want to join N lines and you only need space delimited output   My original answer was xargs -n2 which separates on words rather than lines  -d can be used to split the input by any single character

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A slight variation on glenn jackman s answer using paste  if the value for the -d delimiter option contains more than one character  paste cycles through the characters one by one  and combined with the -s options keeps doing that while processing the same input file   This means that we can use whatever we want to have as the separator plus the escape sequence  n to merge two lines at a time   Using a comma     paste -s -d    n  infile KEY 4048 1736 string 3 KEY 0 1772 string 1 KEY 4192 1349 string 1 KEY 7329 2407 string 2 KEY 0 1774 string 1   and the dollar sign     paste -s -d    n  infile KEY 4048 1736 string 3 KEY 0 1772 string 1 KEY 4192 1349 string 1 KEY 7329 2407 string 2 KEY 0 1774 string 1   What this cannot do is use a separator consisting of multiple characters   As a bonus  if the paste is POSIX compliant  this won t modify the newline of the last line in the file  so for an input file with an odd number of lines like  KEY 4048 1736 string 3 KEY 0 1772 string   paste won t tack on the separation character on the last line     paste -s -d    n  infile KEY 4048 1736 string 3 KEY 0 1772 string

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A more-general solution  allows for more than one follow-up line to be joined  as a shell script   This adds a line between each  because I needed visibility  but that is easily remedied   This example is where the  key  line ended in   and no other lines did      bin bash     join  The rest of the story  when the first line of each   story   matches  PATTERN   Nice for looking for specific changes in bart output    PATTERN       LINEOUT    while read line  do     case  line in          PATTERN                  echo                    echo  LINEOUT                 LINEOUT   line                                                         LINEOUT                    echo                                        LINEOUT   LINEOUT  line                         esac         done

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Simplest way is here    Remove even lines and write it in some temp file 1  Remove odd  lines and write it in some temp file 2  Combine two files in one by using paste command with -d  means delete space      sed  0 2d  file  gt  1  amp  amp  sed  1 2d  file  gt  2  amp  amp  paste -d     1 2

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perl -0pE  s  KEY    K s   d       1 msg   data txt  gt  data merged-lines txt   -0 gobbles the whole file instead of reading it line-by-line  pE wraps code with loop and prints the output  see details in http   perldoc perl org perlrun html   KEY match  KEY  in the beginning of line  followed by non-greedy match of anything       before sequence of    one or more spaces  s  of any kind including line breaks  one or more digit   d   which we capture and later re-insert as  1    followed by the end of line      K conveniently excludes everything on its left hand side from substitution so    1  replaces only 1-2 sequence  see http   perldoc perl org perlre html

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Here is another way with awk   awk  ORS NR 2 FS RS  file       cat file KEY 4048 1736 string 3 KEY 0 1772 string 1 KEY 4192 1349 string 1 KEY 7329 2407 string 2 KEY 0 1774 string 1       awk  ORS NR 2 FS RS  file KEY 4048 1736 string 3 KEY 0 1772 string 1 KEY 4192 1349 string 1 KEY 7329 2407 string 2 KEY 0 1774 string 1   As indicated by Ed Morton in the comments  it is better to add braces for safety and parens for portability    awk    ORS    NR 2   FS   RS    1  file   ORS stands for Output Record Separator  What we are doing here is testing a condition using the NR which stores the line number  If the modulo of NR is a true value   0  then we set the Output Field Separator to the value of FS  Field Separator  which by default is space  else we assign the value of RS  Record Separator  which is newline    If you wish to add   as the separator then use the following    awk    ORS    NR 2         RS    1  file

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You can use awk like this to combine ever 2 pair of lines   awk    if  NR 2    0  line  0  else  printf   s  s n   line   0   line               END  if  length line   print line    flle

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You can also use the following vi command     g    j

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ex  is a scriptable line editor that is in the same family as sed  awk  grep  etc  I think it might be what you are looking for  Many modern vi clone successors also have a vi mode    ex -c   g KEY j  -c  wq  data txt   This says for each line  if it matches  KEY  perform a j oin of the following line  After that command completes  against all lines   issue a w rite and q uit

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paste is good for this job   paste -d      - -  lt  filename

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Try the following line   while read line1  do read line2  echo   line1  line2   done  lt old txt gt new file   Put delimiter in-between    line1  line2     e g  if the delimiter is    then     line1  line2

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There are more ways to kill a dog than hanging   1   awk   key  0  getline  print key       0      Put whatever delimiter you like inside the quotes     References    Originally  Plenty of ways to skin the cat   reverted to an older  potentially originating expression that also has nothing to do with pets

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If Perl is an option  you can try   perl -0pe  s      n     n  1  2 n g  file txt

[bash] How to merge every two lines into one from the command line?

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