命令技巧II

获取绝对路径

好多脚本中，都会有这一段，获取绝对路径,代码如下:

    SOURCE="$0"
    while [ -h "$SOURCE"  ]; do # resolve $SOURCE until the file is no longer a symlink
        DIR="$( cd -P "$( dirname "$SOURCE"  )" && pwd  )"
        SOURCE="$(readlink "$SOURCE")"
        [[ $SOURCE != /*  ]] && SOURCE="$DIR/$SOURCE" # if $SOURCE was a relative symlink, we need to resolve it relative to the path where the symlink file was located
    done
    DIR="$( cd -P "$( dirname "$SOURCE"  )" && pwd  )"

grep 命令

grep -v

grep 中一般会包含grep,需要排除的话，代码如下：

    ps aux|grep nginx|grep -v grep||awk '{print $2}'|xargs -i kill -9 {}

命令详解：grep

grep 和 #？

判断是否查找到，如果有匹配的字符串，返回值是0, 还会打印出匹配字符串的行。如果没有匹配， 会返回1。代码如下：

     ls |grep nginx
     if [ $? -eq 0 ];then
        rm -rf nginx
     fi

判断个数

如果关心统计个数，可以用如下命令(和grep $?有点相似)：

    PACKAGE_CNT=`ls ${UPath} |grep -i "xxxx"|grep ".tar.gz"|wc -l`
    [ $PACKAGE_CNT -gt 1 ] && echo "[ERROR] too many xxx.tar.gz packages in ${UPath}"&& return 1
    [ $PACKAGE_CNT -eq 1 ] && return 0