j aaaaavvvv i aaaaaaaaere root@PC1: /home/test# grep -E " [^a]a{3,5}[^a] " a.txt ## 提取3~5个a的行 i aaaadff k aaarbcd j aaaaavvvv root@PC1: /home/test# grep -E " [^a]a{3,6}[^a] " a.txt ## 提取3~6个a的行 i aaaadff k aaarbcd j aaaaavvvv root@PC1: /home/test# grep -E " [^a]a{3,10}[^a] " a.txt ## 提取3~10个a的行 i aaaadff k aaarbcd j aaaaavvvv i aaaaaaaaere