shell计算字符串长度方法及速度比较

4t2eq

chars=`seq -s " " 100`;
echo $chars
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
echo ${#chars}
291
echo $chars | wc -m
292
echo $(expr length "$chars")
291


time for i in $(seq 11111);do count=${#chars};done;
real    0m0.516s

user    0m0.499s
sys     0m0.017s
[iyunv@52game shell]# time for i in $(seq 11111);do count=`echo ${chars} | wc -m`;done;

real    0m15.773s
user    0m0.473s
sys     0m1.412s
time for i in $(seq 11111);do count=`echo exprlength "${chars}"`;done;        

real    0m5.671s
user    0m0.114s
sys     0m1.856s

结论：尽量用内置功能