26
2017
09

Linux Bash条件判断

   -a file
          True if file exists.
   -b file
          True if file exists and is a block special file.
   -c file
          True if file exists and is a character special file.
   -d file
          True if file exists and 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 exists and is set-group-id.
   -h file
          True if file exists and is a symbolic link.
   -k file
          True if file exists and its ``sticky'' bit is set.
   -p file
          True if file exists and is a named pipe (FIFO).
   -r file
          True if file exists and is readable.
   -s file
          True if file exists and has a size greater than zero.
   -t fd  True if file descriptor fd is open and refers to a terminal.
   -u file
          True if file exists and its set-user-id bit is set.
   -w file
          True if file exists and is writable.
   -x file
          True if file exists and is executable.
   -G file
          True if file exists and is owned by the effective group id.
   -L file
          True if file exists and is a symbolic link.
   -N file
          True if file exists and has been modified since it was last read.
   -O file
          True if file exists and is owned by the effective user id.
   -S file
          True if file exists and is a socket.
   file1 -ef file2
          True if file1 and file2 refer to the same device and inode numbers.
   file1 -nt file2
          True if file1 is newer (according to modification date) than file2, or if file1 exists and file2 does not.
   file1 -ot file2
          True if file1 is older than file2, or if file2 exists and file1 does not.
   -o optname
          True if the shell option optname is enabled.  See the list of options under the description of the -o option to the
          set builtin below.
   -v varname
          True if the shell variable varname is set (has been assigned a value).
   -z string
          True if the length of string is zero.
   string
   -n string
          True if the length of string is non-zero.

   string1 == string2
   string1 = string2
          True if the strings are equal.  = should be used with the test command for POSIX conformance.

   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.

   arg1 OP arg2
          OP is one of -eq, -ne, -lt, -le, -gt, or -ge.  These arithmetic binary operators return true if arg1 is  equal  to,
          not equal to, less than, less than or equal to, greater than, or greater than or equal to arg2, respectively.  Arg1
          and arg2 may be positive or negative integers.
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