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同一表达式中的多个变量扩展修饰符

tag-icon • tag-icon bash array variable-substitution
同一表达式中的多个变量扩展修饰符

为什么以下习惯用法在 bash 4.1.0 中不起作用？

if [[ "${FUNCNAME[*]:1/$FUNCNAME/}" != "${FUNCNAME[*]:1}" ]]

这是在上下文中...

function isCircularRef_test () {
  #
  ### Seems like this should work but it does not.
  ###   if [[ "${FUNCNAME[*]:1/$FUNCNAME/}" != "${FUNCNAME[*]:1}" ]]; then ...
  ### It appears to fail silently and exit the script so neither 'then' nor
  ### 'else' branch executes.
  ### Storing the array into a temporary string variable works. Why necessary?
  #
  printf "%s\n" "VERSION #1"
  local _fna="${FUNCNAME[*]:1}"
  if [[ "${_fna/$FUNCNAME/}" != "${_fna}" ]]
  then
    printf "%s\n" "IS circular reference"
  else
    printf "%s\n" "IS not circular reference"
  fi
  #
  printf "%s\n" "VERSION #2"
  if [[ "${FUNCNAME[*]:1/$FUNCNAME/}" != "${FUNCNAME[*]:1}" ]]
  then
    printf "%s\n" "IS circular reference"
  else
    printf "%s\n" "IS not circular reference"
  fi
}

输出是...

VERSION #1
IS not circular reference
VERSION #2

答案1

这文档shell参数扩展表示替换的语法是：

${parameter/pattern/string}

请注意，第一部分是parameter，而不是另一个包含参数扩展的表达式。所有其他扩展修饰符也是如此。您必须分两步完成：

func1=${FUNCNAME:1}
if [[ ${func1/$FUNCNAME/} != ${func1} ]]

答案2

正如您所说，它不喜欢在同一表达式中使用:index和修饰符：/pattern/

./t.sh: line 19: FUNCNAME[*]: 1/isCircularRef_test/: division by 0 (error token is "/")

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