【shell 】syntax error in conditional expression

【shell 】syntax error in conditional expression

编写shell 脚本时遇见 syntax error in conditional expression 错误，

#!/bin/bash
# cleanup /var/log/message
LOG_DIR=/var/log
ROOT_DID=0
LINES=50
E_XCD=66
E_NOTROOT=67
if [[ "$UID" -ne "$ROOT_UID"]]
then
 echo "Must be root to run this script."
 exit $E_NOTROOT
fi
if [ -n "$1"]
then
    lines=$1
else
   lines=$LINES
fi
.......
[e-mail] # sh test.sh
test.sh: line 12: syntax error in conditional expression
test.sh: line 13: syntax error near `then'
test.sh: line 13: `then'

仔细查看是由于 if 条件中的中括号[ ]与变量之间必须有空格

[e-mail] # vi test.sh
#!/bin/bash
# cleanup /var/log/message
LOG_DIR=/var/log
ROOT_DID=0
LINES=50
E_XCD=66
E_NOTROOT=67
if [[ "$UID" -ne "$ROOT_UID" ]]
then
 echo "Must be root to run this script."
 exit $E_NOTROOT
fi
if [ -n "$1"]
then
    lines=$1
else
   lines=$LINES
fi
.....
"test.sh" 60L, 793C written

修改以后，再次执行成功

[e-mail] # sh test.sh 20
Logs cleaned up