语法：
连接显示。
选项：
-n，显示行号。
-v，显示不可见打印符。
-E，显示“行结束符”（$）。
显示行号
$ cat -n /etc/fstab 1 /dev/VolGroup00/LogVol00 / ext3 defaults 1 1 2 LABEL=/boot /boot ext3 defaults 1 2 3 tmpfs /dev/shm tmpfs defaults 0 0 4 devpts /dev/pts devpts gid=5,mode=620 0 0 5 sysfs /sys sysfs defaults 0 0 6 proc /proc proc defaults 0 0 7 /dev/VolGroup00/LogVol01 swap swap defaults 0 0
打印行末结束符
$ cat -E /etc/fstab/dev/VolGroup00/LogVol00 / ext3 defaults 1 1$LABEL=/boot /boot ext3 defaults 1 2$tmpfs /dev/shm tmpfs defaults 0 0$devpts /dev/pts devpts gid=5,mode=620 0 0$sysfs /sys sysfs defaults 0 0$proc /proc proc defaults 0 0$/dev/VolGroup00/LogVol01 swap swap defaults 0 0$
直接输入命令，就会进入交互模式。直到cat接到一个“文件结束符”时停止交互。
$ cathellohelloare you busy?are you busy?$
重写（case语句的第一个例子“找工作时联系人信息”），使用“文件结束符”，格式化显示交互信息：
#!/bin/bashcat << EOFRecruitment Announcement Are you ready to apply for any job? 1 accounting 2 cashier 3 secretaryPlease enter a number to select the corresponding positions.EOFecho -n "Choice: "read NUMcase $NUM in 1) printf "call mr wang. number is 1124\n" ;; 2) printf "call miss li. number is 1233.\n" ;; 3) printf "call miss ji. number is 1367.\n" ;; *) printf "If you want to make a lot of money, to be a seller. call 1498.\n" ;;esac
打印程序的提示信息：
display_help () { cat << EOFUsage: findTom [OPTION]View the tomcat information.View the home directory of the tomcat program running on the system, andthe project path. Mandatory arguments to long option are mandatory for short options too. -r, --read view the previously running tomcat information. -v, --version view the version --clear when the number of row is greater than 100, then clean-up, and leaving 30 lines. -h, --help display this help and exitE-mail bug reports to: <773805731@qq.com>EOF}
$ ./cat.shRecruitment Announcement Are you ready to apply for any job? 1 accounting 2 cashier 3 secretaryPlease enter a number to select the corresponding positions.Choice:
从程序的输出看出，脚本里的文本格式原样在交互界面显示了。
文件结束符：
Linux: CTRL + d
Windows: CTRL + z