I want to join this two lines but only when after him
I have nothing or a comma

Yes, I know Jonesy, and I'll give him
about one more minute.

this two lines must become
Yes, I know Jonesy, and I'll give him about one more minute.


thank you very much

cat infilke | xargs -d '\n'

sed '/[^[:punct:]],*$/{N;s/\n/ /;}' infile

awk '/[^[:punct:]],*$/{getline $(NF+1)}1' infile

the input is like this

This is my cat
my cat's name is betty

This is my dog
my dog's name is frank

This is my fish
my fish's name is george

This is my goat
my goat's name is adam

when I use xargs then the output is
my goat's name is adamge

when I use sed or awk then the output is
my cat's name is betty
This is my dog
y dog's name is frank
my fish's name is george
This is my goat
y goat's name is adam

but the output must be this
--------------------------------------
This is my cat my cat's name is betty

This is my dog my dog's name is frank

This is my fish my fish's name is george

This is my goat my goat's name is adam

thank you

I presume you mean the other way around.. See if this works:

awk '/[^[:punct:]],*$/{getline $(NF+1)}NF' infile

awk '$1=$1' RS= infile

try this

xargs -L 2 < filename.txt

perl -ne 'if (/^\s+/){print "\n\n"}else{chomp;print "$_ "}' inputfile