字符串操作
${#string}輸出字句的字符個數
${string:position:length}輸出$position開始的length長度的字符
${string:position}
[root@ilove scripts]# liuyifei="i like sanpan i like luo swimming"
[root@ilove scripts]# echo ${#liuyifei}
33
[root@ilove scripts]# echo ${liuyifei:2:4}
like
[root@ilove scripts]# echo ${liuyifei:2}
like sanpan i like luo swimming
====以上實測
${string#substring}從string中從前往後檢索，只要匹配到字符就開始刪除最短匹配
${string##substring}從頭匹配，開始最長刪除
${string%substring}從結尾開始
${string%%substring}從結尾開始，類似以上##
======以上必須必須從一開始就匹配上
[root@ilove scripts]# echo ${liuyifei#like}
i like sanpan i like luo swimming
[root@ilove scripts]# echo ${liuyifei#*like}
sanpan i like luo swimming
[root@ilove scripts]# echo ${liuyifei##*like}
luo swimming
[root@ilove scripts]# echo ${liuyifei%*like}
i like sanpan i like luo swimming
[root@ilove scripts]# echo ${liuyifei%like}
i like sanpan i like luo swimming
[root@ilove scripts]# echo ${liuyifei%like*}
i like sanpan i
[root@ilove scripts]# echo ${liuyifei%%like*}
i========================
${string/substring/replace}替換第一個遇到的匹配的字符
${string/#substring/replace}前綴匹配，必須全部匹配上，替換一長條
${string/%substring/replace}從後往前，替換最後一個遇到的匹配字符，必須全部匹配
[root@ilove scripts]# echo ${liuyifei/like/love}
i love sanpan i like luo swimming
[root@ilove scripts]# echo ${liuyifei/#*like/love}
love luo swimming
[root@ilove scripts]# echo ${liuyifei/%like*/love}
i love
個人總結：在shell變量操作中 出現# % 就必須一直予以匹配才能進行相關操作