为什么此expect脚本在'；它是由cron运行的吗？

我可以使用root或我自己的用户帐户运行这个expect脚本，但是当我使用cron运行它时，总是会出现错误。操作系统是Ubuntu 8.04

错误电子邮件如下：

Date: Thu, 26 Aug 2010 11:50:01 -0400
From: root@supa (Cron Daemon)
To: root@supa
Subject: Cron <root@supa> /home/myusername/bin/uploadmyip

myserver.com
can't read "env(USER)": no such variable
    while executing
"puts $env(USER)"
    (file "/home/myusername/bin/ftpxfer" line 8)

#!/bin/bash
wget -O /dev/stdout http://checkip.dyndns.com/ 2> /dev/null > /tmp/myip.txt && /home/myusername/bin/ftpxfer && chmod 777 /tmp/myip.txt

#!/usr/bin/env expect

if { [lrange $argv 0 0] == ""} {
}

set server myserver.com
puts $server
puts $env(USER)
system "echo "
system pwd
set timeout 5
spawn -noecho ftp $server
expect {
        timeout {puts "ftp to $server timed out"; exit}
        "Name ($server:$env(USER)):"
        }
set timeout 300
send "username\r"
expect "Password:"
send "password\r"
expect "ftp>"
send "binary\r"
expect "ftp>"
send "put /tmp/myip.txt myip.txt\r"
expect "ftp>"
send "^D\r"

expect脚本ftpxfer如下所示

Date: Thu, 26 Aug 2010 11:50:01 -0400
From: root@supa (Cron Daemon)
To: root@supa
Subject: Cron <root@supa> /home/myusername/bin/uploadmyip

myserver.com
can't read "env(USER)": no such variable
    while executing
"puts $env(USER)"
    (file "/home/myusername/bin/ftpxfer" line 8)

#!/bin/bash
wget -O /dev/stdout http://checkip.dyndns.com/ 2> /dev/null > /tmp/myip.txt && /home/myusername/bin/ftpxfer && chmod 777 /tmp/myip.txt

#!/usr/bin/env expect

if { [lrange $argv 0 0] == ""} {
}

set server myserver.com
puts $server
puts $env(USER)
system "echo "
system pwd
set timeout 5
spawn -noecho ftp $server
expect {
        timeout {puts "ftp to $server timed out"; exit}
        "Name ($server:$env(USER)):"
        }
set timeout 300
send "username\r"
expect "Password:"
send "password\r"
expect "ftp>"
send "binary\r"
expect "ftp>"
send "put /tmp/myip.txt myip.txt\r"
expect "ftp>"
send "^D\r"

“sudo crontab-l”的输出

---

答案是，在您的系统上，cron没有设置用户环境变量——cron使用的环境非常小。使用LOGNAME环境变量可能会更幸运。

我刚刚意识到超级用户可能是一个更好的论坛。