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Variable Substitutionby Pigbrain

Variable Substitution

  • 아래 표현식들에는 공백(space)를 포함해선 안된다
  • 콜론(:)은 옵션으로 쓰이며 만약 콜론이 있을 경우 값은 null이 나오지 않는다
FormMeaning
var=value Set each variable var to a value
${var} Use value of var
${var:-value} Use var if set; otherwise, use value
${var:=value} Use var if set; otherwise, use value and assign value to var
${var:=value} Use var if set; otherwise, use value and assign value to var
${#var} Use the length of var
${#*} Use the number of positional parameters
${#@} Use the number of positional parameters
${var:pos} Starting at position pos (0-based) in variable
${var:pos:len} var, extract len characters, or extract rest of string
${var/pat/repl} Use value of var, with first match of pat replaced with repl
${var/pat} Use value of var, with first match of pat deleted
${var/pat/repl} Use value of var, with first match of pat replaced with repl

Example

  1. prompt> var1=apple var2=banana
  2. prompt> echo ${var1} ${var2}
  3. apple banana
  4.  
  5. prompt> echo ${var1:-none} ${var3:-none}
  6. apple none
  7.  
  8. prompt> echo ${var3}
  9.   
  10. prompt> echo ${var3:=computer}
  11. computer  
  12. prompt> echo ${var3}
  13. computer  
  14.  
  15. prompt> echo ${#var3}
  16. 8  
  17.  
  18. prompt> cat test.sh
  19. echo ${#*}
  20. echo ${#@}
  21. prompt> ./test.sh a b c d 
  22. 4
  23. 4
  24.  
  25. prompt> echo ${var3:3}
  26. puter
  27. prompt> echo ${var3:3:2}
  28. pu
  29.  
  30. prompt> echo ${var3/com/moc}
  31. mocputer
  32. prompt> echo ${var3/com}
  33. puter
  34.  
  35. prompt> var4=apple1apple2apple3
  36. prompt> echo ${var4/apple/banana}
  37. banana1apple2apple3
  38. prompt> echo ${var4//apple/banana}
  39. banana1banana2banana3


참고
Published 18 March 2016
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