1234 awk : gensub

1cpuer

# [ /home/soio/1bs/awks ] {2018-05-24 18:30:29}
: 1527157829:0;➜  echo "a b c \n1 2 3"|awk '{gensub(/2/, "100", "g", $2);print $0}'
a b c
1 2 3


# [ /home/soio/1bs/awks ] {2018-05-24 18:30:37}
: 1527157837:0;➜  echo "a b c \n1 2 3"|awk '{d=gensub(/2/, "100", "g", $2);print d}'
b
100


# [ /home/soio/1bs/awks ] {2018-05-24 18:30:58}
: 1527157858:0;➜  echo "a b c \n1 2 3"|awk '{d=gensub(/2/, "100", "g", $0);print d}'
a b c
1 100 3


# [ /home/soio/1bs/awks ] {2018-05-24 18:31:09}
: 1527157869:0;➜  echo "a b c \n1 2 3"|awk '{d=gensub(/2/, "100", "g");print d}'
a b c
1 100 3


第 1 种情况最不懂

christmas1102

gensub(regexp, replacement, how [, target]) #

Search the target string target for matches of the regular expression regexp. If how is a string beginning with ‘g’ or ‘G’ (short for “global”), then replace all matches of regexp with replacement. Otherwise, how is treated as a number indicating which match of regexp to replace. If no target is supplied, use $0. It returns the modified string as the result of the function and the original target string is notchanged.

1cpuer

http://blog.163.com/njut_wangjia ... 425201611100261205/

[root@MySQL ~]# awk 'BEGIN{s="ww";t="hello,world!hello,awk!hello linux!";r="ll";print gensub(r,s,"g1",t)}'
hewwo,world!hewwo,awk!hewwo linux!
[root@MySQL ~]# awk 'BEGIN{s="ww";t="hello,world!hello,awk!hello linux!";r="ll";print gensub(r,s,"G1",t)}'
hewwo,world!hewwo,awk!hewwo linux!

g -and G 作何解
echo "123"| sed "s/2/x/g" # g:全局的意思
echo "123"| sed "s/2/x/G" # G?

1cpuer

buhuile ----------------
ok
--------------------------
如何保存 下面的 ok

baby_神

1. [root@test-01 ~]# echo -e "a b c \n1 2 3"|awk '{$2=gensub(/2/, "100", "g", $2);print $0}'
   
2. a b c
   
3. 1 100 3

复制代码

Shell_HAT

回复 3# 1cpuer


man sed
g G    Copy/append hold space to pattern space.


# echo -e "123\n456"| sed "s/2/x/;G"
1x3

456

#

christmas1102

1. seq 3 | sed '1!G;h;$!d'

复制代码

sed 那个 hold space 不好玩，费脑子
h H g G，小写是覆盖，大写是追加，就算hold space，没东西，追加还是追加，楼上那两个空行，就是hold space追加出来的

1cpuer

# [ /home/soio/1bs/awks ] {2018-05-29 17:02:24}
: 1527584544:0;➜  man awk | grep -n '\<G\>'
871:       %g, %G  Use %e or %f conversion, whichever is shorter, with nonsignificant zeros suppressed.  The %G format uses %E instead of %e.
896:              For %e, %E, %f and %F, the result always contains a decimal point.  For %g, and %G, trailing zeros are not removed from the result.
907:              to the right of the decimal point.  For the %g, and %G formats, it specifies the maximum number of significant digits.  For the %d, %i,  %o,  %u,  %x,
988:       gensub(r, s, h [, t])   Search the target string t for matches of the regular expression r.  If h is a string beginning with g or G, then replace all matches

man awk | grep -A6 '\<G\>' ## 正好找到  gensub(r, s, h [, t])