test 语法
for var in 1 2 3 4 5 6 do echo ${var} done num=10 s=0 for((i=0;i<${num};i=i+1)) do s=${s}+${i} done echo ${s} s=0 for((i=0;i<${num};i=i+1)) do s=$((${s}+${i})) done echo ${s}
变量的默认值 判断
下面的语句表示：如果SLAVE_FILE为空，则值 设置成HADOOP_CONF_DIR}/slaves
[$SLAVE_FILE:-${HADOOP_CONF_DIR}/slaves]
下面的语句是将SLAVE_FILE的语句 变成一行
SLAVE_NAME=$(CAT "$SLAVE_FILE" | SED '#./*$//;/^$/d' )
下面代码读到文件行 while
#!/bin/bash HOST_FILE=/etc/hosts cat ${HOST_FILE} | while read line do echo ${line} done
