file test -n -z等参数

# 注意
# [[ 后面要有个空格，否则会报错
# ]] 前面要有个空格，否则会报错

if [[ -z "${STR1}" ]]; then
  echo "str1 is null"
else
  echo "str1=$ISNULL"
fi

-z 参数 

[ -z STRING ] 判断字符串长度是否为空


STR1=
STR2=""
STR3=''
STR4=NULL

if [[ -z "${STR1}" ]]; then
  echo "str1 is null"
fi

if [[ -z "${STR2}" ]]; then
  echo "str2 is null"
fi

if [[ -z "${STR3}" ]]; then
  echo "str3 is null"
fi

if [[ -z "${STR4}" ]]; then
  echo "str4 is null"
fi

打印结果:

 

-n 参数

[ -n STRING ] 判断字符串长度是否为非空字符串



STR1=
STR2=""
STR3=''
STR4=NULL
STR5=123

# -n是否是空字符串  -n判断是否是非空字符串
if [[ -n "${STR1}" ]]; then
  echo "str1 is not null"
fi


# -n是否是空字符串  -n判断是否是非空字符串
if [[ -n "${STR2}" ]]; then
  echo "str2 is not null"
fi

# -n是否是空字符串  -n判断是否是非空字符串
if [[ -n "${STR3}" ]]; then
  echo "str3 is not null"
fi

# -n是否是空字符串  -n判断是否是非空字符串
if [[ -n "${STR4}" ]]; then
  echo "str4 is not null"
fi

# -n是否是空字符串  -n判断是否是非空字符串
if [[ -n "${STR5}" ]]; then
  echo "str5 is not null"
fi

打印结果:

文件相关参数

# 通过help查看
help test

      -a FILE        True if file exists.
      -b FILE        True if file is block special.
      -c FILE        True if file is character special.
      -d FILE        True if file is a directory.
      -e FILE        True if file exists.
      -f FILE        True if file exists and is a regular file.
      -g FILE        True if file is set-group-id.
      -h FILE        True if file is a symbolic link.
      -L FILE        True if file is a symbolic link.
      -k FILE        True if file has its `sticky' bit set.
      -p FILE        True if file is a named pipe.
      -r FILE        True if file is readable by you.
      -s FILE        True if file exists and is not empty.
      -S FILE        True if file is a socket.
      -t FD          True if FD is opened on a terminal.
      -u FILE        True if the file is set-user-id.
      -w FILE        True if the file is writable by you.
      -x FILE        True if the file is executable by you.
      -O FILE        True if the file is effectively owned by you.
      -G FILE        True if the file is effectively owned by your group.
      -N FILE        True if the file has been modified since it was last read

FILE1 -nt FILE2  True if file1 is newer than file2 (according to modification date).

FILE1 -ot FILE2  True if file1 is older than file2.

FILE1 -ef FILE2  True if file1 is a hard link to file2.

 

      -z STRING      True if string is empty.

      -n STRING
                     STRING      True if string is not empty.

      STRING1 = STRING2
                     True if the strings are equal.
      STRING1 != STRING2
                     True if the strings are not equal.
      STRING1 < STRING2
                     True if STRING1 sorts before STRING2 lexicographically.
      STRING1 > STRING2
                     True if STRING1 sorts after STRING2 lexicographically.

 

-e -d 例子

BASE_PATH=/media

# 判断是否是目录
if [[ -d ${BASE_PATH}/conf/ ]]; then
    echo "$BASE_PATH/conf is directory"
fi


# 判断文件或目录是否存在
if [[ -e ${BASE_PATH}/conf1/ ]]; then
    echo "$BASE_PATH/conf1 is exists"
else
    echo "$BASE_PATH/conf1 is not exists"
fi