shell下文件内容拼接，用逗号分隔

[root@node1 ~]# cat tableName.txt 
hello
hadoop
spark
mapreduce
storm
python

[root@node1 ~]# 

要达到的效果
hello,hadoop,spark,mapreduce,storm,python

[root@node1 ~]#  echo `(cat tableName.txt)` | sed 's/ /,/g'
hello,hadoop,spark,mapreduce,storm,python
[root@node1 ~]# 

 echo `(cat tableName.txt)` | sed 's/ /,/g'