commas

Transform whitespace-separated input, either insert a delimiter or substitue a template string with positional arguments.

Features

• receive stdin, write stdout
• replace whitespace with a delimiter
• OR, substitute a template string with positional arguments
• handles quoted fields, and writes quoted fields

Examples: Template

This is a no-nonsense field substitution tool.

Basic Test

$ echo 'a b c' | commas -t '$2 $3 $1'
b c a

Note that the fields start at 1, not 0. The only reason for this is to align with bash so that you don't have to keep switching your mental model.

Quotes work:

$ echo 'a "b1 b2" c' | commas -t '$2 $3 $1'
b1 b2 c a

Finally, note that whitespace between the incoming values is all ignored, except of course for what is quoted, which will be preserved:

$ echo 'a     "b1    b2"     c' | commas -t '$2 $3 $1'
b1    b2 c a

Here's a practical example. We can list the CPU cache layers:

$ lscpu | grep cache
L1d cache:                            256 KiB (8 instances)
L1i cache:                            256 KiB (8 instances)
L2 cache:                             4 MiB (8 instances)
L3 cache:                             8 MiB (2 instances)

commas can help to reformat this:

$ lscpu | grep cache | commas -t '$1 $3$4'
L1d 256KiB
L1i 256KiB
L2 4MiB
L3 8MiB

Going further, there is support for trimming characters off each of the field values. In the above lscpu output, we can get rid of the : after cache:, and the ( preceding the number of instances:

$ lscpu | grep cache | commas -t '$1 x $3$4 x $5' -s':('
L1d x 256KiB x 8
L1i x 256KiB x 8
L2 x 4MiB x 8
L3 x 8MiB x 2

Examples: Delimiter

The delimiter mode cannot be used together with the template mode. The delimiter mode is a shortcut to "just put commas between the fields" although the delimiter is of course configurable.

Basic Test

$ echo 'a b "c d" e' | commas
a,b,"c d",e

You can choose to lose quotes in the output

$ echo 'a b "c d" e' | commas -l
a,b,c d,e

Extra whitespace

Note that tr does not handle this. Without commas you would have to use sed or awk, or even something bigger like Python or Perl to handle this.

$ echo 'a     b    "c d"        e' | commas
a,b,"c d",e

Pass through to xsv

The xsv tool can do a lot, but it needs comma-separated input. Piping data to xsv was the primary motivation for commas.

Here's an example of field selection with xsv:

$ echo 'a     b    "c d"        e' | commas | xsv select 1,3
a,c d

Reformat selected fields with xsv

$ echo 'a     b    "c d"        e' | commas | xsv select 1,3,4 | xsv fmt -t '|'
a|c d|e