bash - setting variables to inlines with variables in bash?

Question

I'm trying to set the value of a variable to one line of a file, over and over.

for i in {1..5}
   do
       THIS = "grep -m $i'[a-z]' newdict2" | tail -1
       echo $THIS
   done

What's the trick to this black magic?

Answer 1

使用 sed 运行它实际上比使用 tail 和 grep 的 -m 选项更容易：

for i in {1..5}
do
    THIS=$(grep -e '[a-z]' newdict2 | sed -ne "${i}p")
    echo "$THIS"
done

如果从 1 到 x 开始，其他解决方法是通过循环读行：

while IFS= read -r THIS; do
    echo "$THIS"
done < <(grep -e '[a-z]' newdict2)

并通过 awk：

while IFS= read -r THIS; do
    echo "$THIS"
done < (awk '/[a-z]/ && ++i <= 5' newdict2)

另一个初始值不同的 awk 版本：

while IFS= read -r THIS; do
    echo "$THIS"
done < (awk 'BEGIN { i = 2 } /[a-z]/ && i++ <= 5' newdict2)

Answer 2

最好找到一次，然后循环遍历它们。

grep -m "$i" '[a-z]' newdict |
nl |
while read i THIS; do
    echo "$THIS"
done

如果您不需要$i循环内的任何内容，请删除nl并仅read THIS.

还要注意在变量插值周围使用双引号。