Shell: ECHO does not display multiple spaces in the variable.

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When the echo variable is in shell, only one space is printed in the variable, as shown below:

 
1 Sh-3.2$ TMP="A B d"
2 Sh-3.2$ Echo $ TMP
3 A B d
 

The solution is to add double quotation marks to the variable, as shown below:

1H-3.2$ TMP="A B d"
2Sh-3.2$ Echo"$ TMP"
3A B d
 

As for the reason, you need to understand the shell parsing process:

1. Replace variable
2. Execute Command
3. Divide the parameters after the command by IFS, and use the section enclosed by "" and "as a parameter of the command.

The execution process of ECHO $ TMP is:

1. Replace variable: echo a B D
2. Run echo a B D.
3. Divide parameters A, B, and d after the echo command by IFS

Therefore, the output is a B D, and only one space is displayed.

ObserveCodeAlso known

 1   Sh  -  3.2  $ TMP  =  "  A B d  "  
  2   Sh -  3.2  $ Echo $ TMP
  3   A B d
  4   Sh  -  3.2  $ Echo a B c
  5   A B C
  6   Sh  -  3.2  $ Echo "  $ TMP  "  
  7   A B d
  8   Sh  -  3.2  $ Echo  "  A B C  "  
  9   A B C