[linux] 使用 bash 合併兩行變成一行 How to merge two lines into one line

How to merge two lines into one line

怎麼使用 bash 合併兩行變成一行呢?
簡單提供兩種作法 可以使用 xargs 或是 awk

 % cat /tmp/ex                                                                                   
1
2
3
4
5
6

  % cat /tmp/ex | xargs -n 2 -d '\n'                                                               
1 2
3 4
5 6


       -n max-args, --max-args=max-args
              Use at most max-args arguments per command line.  Fewer than  max-args  arguments  will  be
              used  if  the size (see the -s option) is exceeded, unless the -x option is given, in which
              case xargs will exit.

       --delimiter=delim, -d delim
              Input items are terminated by the specified character.  The specified delimiter  may  be  a
              single  character, a C-style character escape such as \n, or an octal or hexadecimal escape
              code.  Octal and hexadecimal escape  codes  are  understood  as  for  the  printf  command.
              Multibyte  characters  are  not supported.  When processing the input, quotes and backslash
              are not special; every character in the input is taken literally.  The -d  option  disables
              any  end-of-file string, which is treated like any other argument.  You can use this option
              when the input consists of simply newline-separated items, although  it  is  almost  always
              better to design your program to use --null where this is possible.


% cat /tmp/ex | awk 'NR%2{printf "%s ",$0;next;}{print;}'
1 2
3 4
5 6


              NR        current record number in the total input stream.

      There are two output statements, print and printf.

              print  writes $0  ORS to standard output.

              print expr1, expr2, ..., exprn
                     writes expr1 OFS expr2 OFS ... exprn ORS to standard  output.   Numeric  expressions
                     are converted to string with OFMT.

              printf format, expr-list
                     duplicates  the  printf C library function writing to standard output.  The complete
                     ANSI C format specifications are recognized with conversions %c, %d, %e, %E, %f, %g,
                     %G, %i, %o, %s, %u, %x, %X and %%, and conversion qualifiers h and l.

      Program flow at the pattern {action} level can be changed with the

            next
            exit  opt_expr

       statements.   A  next  statement  causes  the  next input record to be read and pattern testing to
       restart with the first pattern {action} pair in the program.  An exit statement  causes  immediate
       execution  of the END actions or program termination if there are none or if the exit occurs in an
       END action.  The opt_expr sets the exit value of the program unless overridden by a later exit  or
       subsequent error.