Question

我经常在文件.sh的Shell脚本中发现以下条件条件：

if [ -n "condition" ]; then ...
if [ -z "condition "]; then ...
if [ -x "condition" ]; then ...
if [ -L "condition" ]; then ...
if [ -d "condition" ]; then ...

这些-n, -z, -x, -L, -d是函数，或者它的名字和目的是什么？

Answer 1

恕我直言，最好的方法是您只需为所有这些详细信息进行man test。那里很好解释。以下是手册页中的文本。对于BASH条件表达式，一次也找不到链接https://www.gnu.org/software/bash/manual/html_node/Bash-Conditional-Expressions.html。

   -b FILE
          FILE exists and is block special

   -c FILE
          FILE exists and is character special

   -d FILE
          FILE exists and is a directory

   -e FILE
          FILE exists

   -f FILE
          FILE exists and is a regular file

   -g FILE
          FILE exists and is set-group-ID

   -G FILE
          FILE exists and is owned by the effective group ID

   -h FILE
          FILE exists and is a symbolic link (same as -L)

   -k FILE
          FILE exists and has its sticky bit set

   -L FILE
          FILE exists and is a symbolic link (same as -h)

   -O FILE
          FILE exists and is owned by the effective user ID

   -p FILE
          FILE exists and is a named pipe

   -r FILE
          FILE exists and read permission is granted

   -s FILE
          FILE exists and has a size greater than zero

   -S FILE
          FILE exists and is a socket

   -t FD  file descriptor FD is opened on a terminal

   -u FILE
          FILE exists and its set-user-ID bit is set

   -w FILE
          FILE exists and write permission is granted

   -x FILE
          FILE exists and execute (or search) permission is granted

对于man test中的表达式，给出：

   ( EXPRESSION )
          EXPRESSION is true

   ! EXPRESSION
          EXPRESSION is false

   EXPRESSION1 -a EXPRESSION2
          both EXPRESSION1 and EXPRESSION2 are true

   EXPRESSION1 -o EXPRESSION2
          either EXPRESSION1 or EXPRESSION2 is true

   -n STRING
          the length of STRING is nonzero

   STRING equivalent to -n STRING

   -z STRING
          the length of STRING is zero

   STRING1 = STRING2
          the strings are equal

   STRING1 != STRING2
          the strings are not equal

   INTEGER1 -eq INTEGER2
          INTEGER1 is equal to INTEGER2

   INTEGER1 -ge INTEGER2
          INTEGER1 is greater than or equal to INTEGER2

对于条件表达式，请输入man bash，它也提供如下信息。

条件表达 [[复合命令和测试以及[内置命令]使用条件表达式来测试文件属性和执行字符串和算术比较。表达式由以下一元或二进制原语组成。如果任何文件自变量之一主要是格式为/ dev / fd / n，然后检查文件描述符n。如果其中一个原语的文件参数是/ dev / stdin之一， / dev / stdout，或 / dev / stderr，分别检查文件描述符0、1或2。
   Unless otherwise specified, primaries that operate on files follow symbolic links and operate on the target of the link, rather 
比链接本身。
   When used with [[, The < and > operators sort lexicographically using the current locale.

Shell脚本中-n，-z，-x，-L，-d等的含义是什么？

1 个答案: