Question

我在最后一个命令行中发现了以下bash行为。对我来说，这是完全出乎意料的。

$ set | grep ^BASH_VERSINFO             # Show the array
BASH_VERSINFO=([0]="3" [1]="2" [2]="25" [3]="1" [4]="release" [5]="x86_64-redhat-linux-gnu")

$ echo "${BASH_VERSINFO[@]}"             # Print all array
3 2 25 1 release x86_64-redhat-linux-gnu

$ echo "${BASH_VERSINFO[@]%e}"           # Print all array removing final 'e' of every member
3 2 25 1 releas x86_64-redhat-linux-gnu

$ i=4; echo "${BASH_VERSINFO[i]}"        # Print an array member
release
$ i=4; echo "${BASH_VERSINFO[i++]}"      # Print an array member and increase the 'i' variable
release
$ i=4; echo "${BASH_VERSINFO[i]%e}"      # Print an array member removing the final 'e'
releas
$ i=4; echo "${BASH_VERSINFO[i++]%e}"    # Why does bash use the next member?
x86_64-redhat-linux-gnu

似乎bash预先增加'i'变量。

类似奇怪的行为：

$ i=5; echo "${BASH_VERSINFO[--i]}"    # Print array member ${BASH_VERSINFO[4]}. 'i' is descreased one time.
release
$ i=5; echo "${BASH_VERSINFO[--i]%e}"  # Print array member ${BASH_VERSINFO[3]%e}. 'i' is descreased two times.
1

有人能告诉我这种行为吗？

提前完成

Answer 1

这似乎是一个已修复的错误，可能是这个：

（来自bash ChangeLog - bash-4.2-alpha和bash-4.1-release之间的变化）

修复了算术扩展中导致数组中索引的错误扩展在某些情况下进行两次评估。

WORKSFORME：

$ echo "${BASH_VERSINFO[*]}"
4 2 42 1 release i586-pc-linux-gnu
$ i=4; echo "${BASH_VERSINFO[i++]}"; echo "$i"
release
5
$ i=4; echo "${BASH_VERSINFO[i++]%e}"; echo "$i"
releas
5

bash：意外的数组成员句柄

1 个答案: