Simple printf, awk and sed

Replace a char in a string 

echo $SN | sed 's/-/_/g'

Extract a column

 [root@mail slaves]# ll -tr | grep -v total
-rw-------  1 root  root  18196 Mar  1 17:22 example.com.hosts
-rw-r--r--  1 root  root    172 Mar  6 16:55 example.com.hosts.bak
-rw-------  1 named named   358 Mar 11 08:34 sec.example.com
[root@mail slaves]# ll -tr | grep -v total | awk -F" " '{print $9}'
example.com.hosts
example.com.hosts.bak
sec.example.com

Replace a char every token

[root@mail filelist]# ls
f_1363024548  f_1363024566  f_1363024569  f_1363024572
f_1363024564  f_1363024567  f_1363024570  f_1363024573
f_1363024565  f_1363024568  f_1363024571

[root@mail filelist]# for f in `ls`; do
> echo $f | sed 's/f/a/g'
> done
a_1363024548
a_1363024564
a_1363024565
a_1363024566
a_1363024567
a_1363024568
a_1363024569
a_1363024570
a_1363024571
a_1363024572
a_1363024573

Replace char(s) in a file

[root@mail filelist]# cat file.txt | sed 's/ffff/1/g'
abcd1abcd1
efgh1eeef

Print strings in specified format

[root@mail filelist]# printf "%s %s\n" "abc" "def"
abc def

Replace a space in a string to a return "\n"

[root@localhost ~]# str="abc def ijk"
[root@localhost ~]# echo $str
abc def ijk

[root@localhost ~]# echo $str | sed 's/\s/\n/g'
abc
def
ijk

Extract Token from a string

note that the regex is using greedy match, if we use gender=\(.*\), it will map till the place before school="ics"

e.g str="name=nana gender=girl age=5 school=ics"
sed -n 's/.*[[:blank:]]gender=\([a-z]*\)[[:blank:]].*/\1/p'  $str