如何解决 Linux If-Else 语句语法错误？

Question

I am trying to check whether a directory already exists or not inside a case-control statement. But it is giving an error in 'then' statement.

case $choice in
1)echo "Enter directory name: "
  read dname
  mkdir $dname
  if[-d "$dname"]
  then
     echo "$dname directory already exists."
  else
     echo "$dname directory successfully created."
  fi
  read
  ;;

error message:

uan.sh: line 13: syntax error near unexpected token `then'
uan.sh: line 13: `  then'

Answer 1

The parser is seeing then outside of an if statement, because you don't have the keyword if in a command position. You have the word if[-d which the parser accepts as an ordinary command name; the parser doesn't know or care whether the command actually exists or not.

Whitespace is important:

if [ -d "$dname" ]

The brackets are supposed to remind you of syntax, but have probably caused more trouble than they have ever saved. [ is the command, and it requires ] as its final argument. Using the name test is much simpler and doesn't lull you into thinking the brackets are somehow special to the parser:

if test -d "$dname"