shell学习笔记

文件表达式

# man test

EXPRESSION	DESCRIPTION	EXAMPLE
-n STRING	the length of STRING is nonzero	[  -n "$STR" ]
-z STRING	the length of STRING is zero	[ -z ${STR} ]
-f FILE	FILE exists and is a regular file	[ ! -f ${FILE_1} ] || [ ! -f ${FILE_2} ]
-h FILE	FILE exists and is a symbolic link (same as -L)	[ -h "$FILE" ]

命令

readlink ${FILE}  示例: if [ -h "$LOCAL" ]; then LOCAL=$(readlink ${LOCAL}) fi
readlink -f ${FILE}  示例: MYSELF=$(readlink -f ${0})

dirname ${FILE}

id -u  示例: [ "$(id -u)" != "0" ]

md5sum -c $md5sum_file  示例: md5sum --quiet -c $md5sum_file