Combine multiple fields with awk-CodePudding

I want to get abc/123/efg from abc/123/efg/456

I try to get the first NF - 1 fields and concatenate them with /.

So I do:

echo abc/123/efg/456 | awk -F "/" 'BEGIN {OFS="/"} {for(i=1;i<=NF-1;i  ) {var = var $i} END {print var}'

However, it did not work as I expected.

What am I doing wrong?

Is there any way to do this more elegantly?

CodePudding user response：

To fix your code:

echo "abc/123/efg/456" | awk -F "/" 'BEGIN {OFS="/"} {
  for(i=1;i<NF;i  ) var = (var ? var OFS : "") $i
}
END {print var}'

As an alternative, you might for example remove starting from the last occurrence of / until the end of the string.

echo "abc/123/efg/456" | awk '{sub("/[^/]*$", "")}1'

Output

abc/123/efg

CodePudding user response：

One idea would be to decrement NF, eg:

$ echo 'abc/123/efg/456' | awk 'BEGIN {FS=OFS="/"} NF--'
abc/123/efg

Whether or not this is the 'best' solution is going to depend on the rest of your coding requirements, ie:

if you're doing additional work within awk then this could be combined with other awk scripting
if the only purpose of awk is to strip off the last field then this may be overkill and a better (?) solution may be to perform the operation in bash (eg, parameter substitution, dirname, etc)

CodePudding user response：

Here is my approach: Remove the last field. Yes, it is that easy. The code:

echo "abc/123/efg/456" | awk -F/ -vOFS=/ '{NF--; print}'

Notes

The flag -F/ specifies the input field separator
The flag -vOFS=/ specifies the output field separator
The NF-- statement decreases the number of fields by one
The print statement prints the whole record (line) after the removal of the last field

CodePudding user response：

simplest approach (if you're concerned with extra blank lines)

echo 'abc/123/efg/456\n\n' |

 nawk 'NF=(-_<NF) * 3' FS='[/]' OFS='/'    
 mawk 'NF * (NF = 3)' FS='[/]' OFS='/'

abc/123/efg

if you're concerned about decrementing NF all the way to negative zone :

mawk2 'NF -= !!NF' FS='[/]' OFS='/'

or just have FS OFS scrub it for u, risk free :

 gawk NF=NF FS='[/][^/]*$' OFS=

if those represent nested folders/directories of any kind, then use this trick to get a 2D tree view :

 nawk 'NF-=!!NF' FS='[/]' OFS='\f\b/'

abc
  /123
     /efg