gawk字符串函数 tolower 和 toupper 仅在gawk中可用. 顾名思意函数转换给定字符串到小写或大写，如下所示：
$ cat items.txt
101,HD Camcorder,Video,210,10
102,Refrigerator,Appliance,850,2
103,MP3 Player,Audio,270,15
104,Tennis Racket,Sports,190,20
105,Laser Printer,Office,475,5
$ awk '{print tolower($0)}' items.txt
101,hd camcorder,video,210,10
102,refrigerator,appliance,850,2
103,mp3 player,audio,270,15
104,tennis racket,sports,190,20
105,laser printer,office,475,5
大写：
$ awk '{print toupper($0)}' items.txt
101,HD CAMCORDER,VIDEO,210,10
102,REFRIGERATOR,APPLIANCE,850,2
103,MP3 PLAYER,AUDIO,270,15
104,TENNIS RACKET,SPORTS,190,20
105,LASER PRINTER,OFFICE,475,5