1.my shell file is
[root#node3 script]# cat hi.sh
#!/bin/bash
strings="sdsf sdsda sdsadx"
echo `awk "{print substr($0,0,9)}"<<<$strings`
2.exe my shell file
[root#node3 script]# sh hi.sh
awk: {print substr(hi.sh,0,9)}
awk: ^ syntax error
awk: 致命错误: 0 是 substr 的无效参数个数
so how to use the awk's $0 in shell file ?
the $0 default file's name .
another ques. i want use the var $0 about awk but the another $variable in the shell file.what should i do ?
$ cat hi.sh
#!/bin/bash
strings="sdsf sdsda sdsadx"
num=9
echo \`awk '{print substr($0,0,$num)}' <<< $strings\`
The problem with your script is use of double quotes in awk. Replace them with single quotes.
When you use double quotes, the $0 inside it is treated as first argument to the script, which in this case is script name hi.sh. If you use single quotes, you can use $0 as awk argument to display whole row.
Also echo is not needed here, you can just use awk '{print substr($0,0,9)}' <<< $strings
$ cat hi.sh
#!/bin/bash
strings="sdsf sdsda sdsadx"
#echo `awk '{print substr($0,0,9)}' <<< $strings` --echo not needed
awk '{print substr($0,0,9)}' <<< $strings
$
$ sh hi.sh
sdsf sdsd
Related
I found some ways to pass external shell variables to an awk script, but I'm confused about ' and ".
First, I tried with a shell script:
$ v=123test
$ echo $v
123test
$ echo "$v"
123test
Then tried awk:
$ awk 'BEGIN{print "'$v'"}'
$ 123test
$ awk 'BEGIN{print '"$v"'}'
$ 123
Why is the difference?
Lastly I tried this:
$ awk 'BEGIN{print " '$v' "}'
$ 123test
$ awk 'BEGIN{print ' "$v" '}'
awk: cmd. line:1: BEGIN{print
awk: cmd. line:1: ^ unexpected newline or end of string
I'm confused about this.
#Getting shell variables into awk
may be done in several ways. Some are better than others. This should cover most of them. If you have a comment, please leave below. v1.5
Using -v (The best way, most portable)
Use the -v option: (P.S. use a space after -v or it will be less portable. E.g., awk -v var= not awk -vvar=)
variable="line one\nline two"
awk -v var="$variable" 'BEGIN {print var}'
line one
line two
This should be compatible with most awk, and the variable is available in the BEGIN block as well:
If you have multiple variables:
awk -v a="$var1" -v b="$var2" 'BEGIN {print a,b}'
Warning. As Ed Morton writes, escape sequences will be interpreted so \t becomes a real tab and not \t if that is what you search for. Can be solved by using ENVIRON[] or access it via ARGV[]
PS If you have vertical bar or other regexp meta characters as separator like |?( etc, they must be double escaped. Example 3 vertical bars ||| becomes -F'\\|\\|\\|'. You can also use -F"[|][|][|]".
Example on getting data from a program/function inn to awk (here date is used)
awk -v time="$(date +"%F %H:%M" -d '-1 minute')" 'BEGIN {print time}'
Example of testing the contents of a shell variable as a regexp:
awk -v var="$variable" '$0 ~ var{print "found it"}'
Variable after code block
Here we get the variable after the awk code. This will work fine as long as you do not need the variable in the BEGIN block:
variable="line one\nline two"
echo "input data" | awk '{print var}' var="${variable}"
or
awk '{print var}' var="${variable}" file
Adding multiple variables:
awk '{print a,b,$0}' a="$var1" b="$var2" file
In this way we can also set different Field Separator FS for each file.
awk 'some code' FS=',' file1.txt FS=';' file2.ext
Variable after the code block will not work for the BEGIN block:
echo "input data" | awk 'BEGIN {print var}' var="${variable}"
Here-string
Variable can also be added to awk using a here-string from shells that support them (including Bash):
awk '{print $0}' <<< "$variable"
test
This is the same as:
printf '%s' "$variable" | awk '{print $0}'
P.S. this treats the variable as a file input.
ENVIRON input
As TrueY writes, you can use the ENVIRON to print Environment Variables.
Setting a variable before running AWK, you can print it out like this:
X=MyVar
awk 'BEGIN{print ENVIRON["X"],ENVIRON["SHELL"]}'
MyVar /bin/bash
ARGV input
As Steven Penny writes, you can use ARGV to get the data into awk:
v="my data"
awk 'BEGIN {print ARGV[1]}' "$v"
my data
To get the data into the code itself, not just the BEGIN:
v="my data"
echo "test" | awk 'BEGIN{var=ARGV[1];ARGV[1]=""} {print var, $0}' "$v"
my data test
Variable within the code: USE WITH CAUTION
You can use a variable within the awk code, but it's messy and hard to read, and as Charles Duffy points out, this version may also be a victim of code injection. If someone adds bad stuff to the variable, it will be executed as part of the awk code.
This works by extracting the variable within the code, so it becomes a part of it.
If you want to make an awk that changes dynamically with use of variables, you can do it this way, but DO NOT use it for normal variables.
variable="line one\nline two"
awk 'BEGIN {print "'"$variable"'"}'
line one
line two
Here is an example of code injection:
variable='line one\nline two" ; for (i=1;i<=1000;++i) print i"'
awk 'BEGIN {print "'"$variable"'"}'
line one
line two
1
2
3
.
.
1000
You can add lots of commands to awk this way. Even make it crash with non valid commands.
One valid use of this approach, though, is when you want to pass a symbol to awk to be applied to some input, e.g. a simple calculator:
$ calc() { awk -v x="$1" -v z="$3" 'BEGIN{ print x '"$2"' z }'; }
$ calc 2.7 '+' 3.4
6.1
$ calc 2.7 '*' 3.4
9.18
There is no way to do that using an awk variable populated with the value of a shell variable, you NEED the shell variable to expand to become part of the text of the awk script before awk interprets it. (see comment below by Ed M.)
Extra info:
Use of double quote
It's always good to double quote variable "$variable"
If not, multiple lines will be added as a long single line.
Example:
var="Line one
This is line two"
echo $var
Line one This is line two
echo "$var"
Line one
This is line two
Other errors you can get without double quote:
variable="line one\nline two"
awk -v var=$variable 'BEGIN {print var}'
awk: cmd. line:1: one\nline
awk: cmd. line:1: ^ backslash not last character on line
awk: cmd. line:1: one\nline
awk: cmd. line:1: ^ syntax error
And with single quote, it does not expand the value of the variable:
awk -v var='$variable' 'BEGIN {print var}'
$variable
More info about AWK and variables
Read this faq.
It seems that the good-old ENVIRON awk built-in hash is not mentioned at all. An example of its usage:
$ X=Solaris awk 'BEGIN{print ENVIRON["X"], ENVIRON["TERM"]}'
Solaris rxvt
You could pass in the command-line option -v with a variable name (v) and a value (=) of the environment variable ("${v}"):
% awk -vv="${v}" 'BEGIN { print v }'
123test
Or to make it clearer (with far fewer vs):
% environment_variable=123test
% awk -vawk_variable="${environment_variable}" 'BEGIN { print awk_variable }'
123test
You can utilize ARGV:
v=123test
awk 'BEGIN {print ARGV[1]}' "$v"
Note that if you are going to continue into the body, you will need to adjust
ARGC:
awk 'BEGIN {ARGC--} {print ARGV[2], $0}' file "$v"
I just changed #Jotne's answer for "for loop".
for i in `seq 11 20`; do host myserver-$i | awk -v i="$i" '{print "myserver-"i" " $4}'; done
I had to insert date at the beginning of the lines of a log file and it's done like below:
DATE=$(date +"%Y-%m-%d")
awk '{ print "'"$DATE"'", $0; }' /path_to_log_file/log_file.log
It can be redirect to another file to save
Pro Tip
It could come handy to create a function that handles this so you dont have to type everything every time. Using the selected solution we get...
awk_switch_columns() {
cat < /dev/stdin | awk -v a="$1" -v b="$2" " { t = \$a; \$a = \$b; \$b = t; print; } "
}
And use it as...
echo 'a b c d' | awk_switch_columns 2 4
Output:
a d c b
I found some ways to pass external shell variables to an awk script, but I'm confused about ' and ".
First, I tried with a shell script:
$ v=123test
$ echo $v
123test
$ echo "$v"
123test
Then tried awk:
$ awk 'BEGIN{print "'$v'"}'
$ 123test
$ awk 'BEGIN{print '"$v"'}'
$ 123
Why is the difference?
Lastly I tried this:
$ awk 'BEGIN{print " '$v' "}'
$ 123test
$ awk 'BEGIN{print ' "$v" '}'
awk: cmd. line:1: BEGIN{print
awk: cmd. line:1: ^ unexpected newline or end of string
I'm confused about this.
#Getting shell variables into awk
may be done in several ways. Some are better than others. This should cover most of them. If you have a comment, please leave below. v1.5
Using -v (The best way, most portable)
Use the -v option: (P.S. use a space after -v or it will be less portable. E.g., awk -v var= not awk -vvar=)
variable="line one\nline two"
awk -v var="$variable" 'BEGIN {print var}'
line one
line two
This should be compatible with most awk, and the variable is available in the BEGIN block as well:
If you have multiple variables:
awk -v a="$var1" -v b="$var2" 'BEGIN {print a,b}'
Warning. As Ed Morton writes, escape sequences will be interpreted so \t becomes a real tab and not \t if that is what you search for. Can be solved by using ENVIRON[] or access it via ARGV[]
PS If you have vertical bar or other regexp meta characters as separator like |?( etc, they must be double escaped. Example 3 vertical bars ||| becomes -F'\\|\\|\\|'. You can also use -F"[|][|][|]".
Example on getting data from a program/function inn to awk (here date is used)
awk -v time="$(date +"%F %H:%M" -d '-1 minute')" 'BEGIN {print time}'
Example of testing the contents of a shell variable as a regexp:
awk -v var="$variable" '$0 ~ var{print "found it"}'
Variable after code block
Here we get the variable after the awk code. This will work fine as long as you do not need the variable in the BEGIN block:
variable="line one\nline two"
echo "input data" | awk '{print var}' var="${variable}"
or
awk '{print var}' var="${variable}" file
Adding multiple variables:
awk '{print a,b,$0}' a="$var1" b="$var2" file
In this way we can also set different Field Separator FS for each file.
awk 'some code' FS=',' file1.txt FS=';' file2.ext
Variable after the code block will not work for the BEGIN block:
echo "input data" | awk 'BEGIN {print var}' var="${variable}"
Here-string
Variable can also be added to awk using a here-string from shells that support them (including Bash):
awk '{print $0}' <<< "$variable"
test
This is the same as:
printf '%s' "$variable" | awk '{print $0}'
P.S. this treats the variable as a file input.
ENVIRON input
As TrueY writes, you can use the ENVIRON to print Environment Variables.
Setting a variable before running AWK, you can print it out like this:
X=MyVar
awk 'BEGIN{print ENVIRON["X"],ENVIRON["SHELL"]}'
MyVar /bin/bash
ARGV input
As Steven Penny writes, you can use ARGV to get the data into awk:
v="my data"
awk 'BEGIN {print ARGV[1]}' "$v"
my data
To get the data into the code itself, not just the BEGIN:
v="my data"
echo "test" | awk 'BEGIN{var=ARGV[1];ARGV[1]=""} {print var, $0}' "$v"
my data test
Variable within the code: USE WITH CAUTION
You can use a variable within the awk code, but it's messy and hard to read, and as Charles Duffy points out, this version may also be a victim of code injection. If someone adds bad stuff to the variable, it will be executed as part of the awk code.
This works by extracting the variable within the code, so it becomes a part of it.
If you want to make an awk that changes dynamically with use of variables, you can do it this way, but DO NOT use it for normal variables.
variable="line one\nline two"
awk 'BEGIN {print "'"$variable"'"}'
line one
line two
Here is an example of code injection:
variable='line one\nline two" ; for (i=1;i<=1000;++i) print i"'
awk 'BEGIN {print "'"$variable"'"}'
line one
line two
1
2
3
.
.
1000
You can add lots of commands to awk this way. Even make it crash with non valid commands.
One valid use of this approach, though, is when you want to pass a symbol to awk to be applied to some input, e.g. a simple calculator:
$ calc() { awk -v x="$1" -v z="$3" 'BEGIN{ print x '"$2"' z }'; }
$ calc 2.7 '+' 3.4
6.1
$ calc 2.7 '*' 3.4
9.18
There is no way to do that using an awk variable populated with the value of a shell variable, you NEED the shell variable to expand to become part of the text of the awk script before awk interprets it. (see comment below by Ed M.)
Extra info:
Use of double quote
It's always good to double quote variable "$variable"
If not, multiple lines will be added as a long single line.
Example:
var="Line one
This is line two"
echo $var
Line one This is line two
echo "$var"
Line one
This is line two
Other errors you can get without double quote:
variable="line one\nline two"
awk -v var=$variable 'BEGIN {print var}'
awk: cmd. line:1: one\nline
awk: cmd. line:1: ^ backslash not last character on line
awk: cmd. line:1: one\nline
awk: cmd. line:1: ^ syntax error
And with single quote, it does not expand the value of the variable:
awk -v var='$variable' 'BEGIN {print var}'
$variable
More info about AWK and variables
Read this faq.
It seems that the good-old ENVIRON awk built-in hash is not mentioned at all. An example of its usage:
$ X=Solaris awk 'BEGIN{print ENVIRON["X"], ENVIRON["TERM"]}'
Solaris rxvt
You could pass in the command-line option -v with a variable name (v) and a value (=) of the environment variable ("${v}"):
% awk -vv="${v}" 'BEGIN { print v }'
123test
Or to make it clearer (with far fewer vs):
% environment_variable=123test
% awk -vawk_variable="${environment_variable}" 'BEGIN { print awk_variable }'
123test
You can utilize ARGV:
v=123test
awk 'BEGIN {print ARGV[1]}' "$v"
Note that if you are going to continue into the body, you will need to adjust
ARGC:
awk 'BEGIN {ARGC--} {print ARGV[2], $0}' file "$v"
I just changed #Jotne's answer for "for loop".
for i in `seq 11 20`; do host myserver-$i | awk -v i="$i" '{print "myserver-"i" " $4}'; done
I had to insert date at the beginning of the lines of a log file and it's done like below:
DATE=$(date +"%Y-%m-%d")
awk '{ print "'"$DATE"'", $0; }' /path_to_log_file/log_file.log
It can be redirect to another file to save
Pro Tip
It could come handy to create a function that handles this so you dont have to type everything every time. Using the selected solution we get...
awk_switch_columns() {
cat < /dev/stdin | awk -v a="$1" -v b="$2" " { t = \$a; \$a = \$b; \$b = t; print; } "
}
And use it as...
echo 'a b c d' | awk_switch_columns 2 4
Output:
a d c b
I found some ways to pass external shell variables to an awk script, but I'm confused about ' and ".
First, I tried with a shell script:
$ v=123test
$ echo $v
123test
$ echo "$v"
123test
Then tried awk:
$ awk 'BEGIN{print "'$v'"}'
$ 123test
$ awk 'BEGIN{print '"$v"'}'
$ 123
Why is the difference?
Lastly I tried this:
$ awk 'BEGIN{print " '$v' "}'
$ 123test
$ awk 'BEGIN{print ' "$v" '}'
awk: cmd. line:1: BEGIN{print
awk: cmd. line:1: ^ unexpected newline or end of string
I'm confused about this.
#Getting shell variables into awk
may be done in several ways. Some are better than others. This should cover most of them. If you have a comment, please leave below. v1.5
Using -v (The best way, most portable)
Use the -v option: (P.S. use a space after -v or it will be less portable. E.g., awk -v var= not awk -vvar=)
variable="line one\nline two"
awk -v var="$variable" 'BEGIN {print var}'
line one
line two
This should be compatible with most awk, and the variable is available in the BEGIN block as well:
If you have multiple variables:
awk -v a="$var1" -v b="$var2" 'BEGIN {print a,b}'
Warning. As Ed Morton writes, escape sequences will be interpreted so \t becomes a real tab and not \t if that is what you search for. Can be solved by using ENVIRON[] or access it via ARGV[]
PS If you have vertical bar or other regexp meta characters as separator like |?( etc, they must be double escaped. Example 3 vertical bars ||| becomes -F'\\|\\|\\|'. You can also use -F"[|][|][|]".
Example on getting data from a program/function inn to awk (here date is used)
awk -v time="$(date +"%F %H:%M" -d '-1 minute')" 'BEGIN {print time}'
Example of testing the contents of a shell variable as a regexp:
awk -v var="$variable" '$0 ~ var{print "found it"}'
Variable after code block
Here we get the variable after the awk code. This will work fine as long as you do not need the variable in the BEGIN block:
variable="line one\nline two"
echo "input data" | awk '{print var}' var="${variable}"
or
awk '{print var}' var="${variable}" file
Adding multiple variables:
awk '{print a,b,$0}' a="$var1" b="$var2" file
In this way we can also set different Field Separator FS for each file.
awk 'some code' FS=',' file1.txt FS=';' file2.ext
Variable after the code block will not work for the BEGIN block:
echo "input data" | awk 'BEGIN {print var}' var="${variable}"
Here-string
Variable can also be added to awk using a here-string from shells that support them (including Bash):
awk '{print $0}' <<< "$variable"
test
This is the same as:
printf '%s' "$variable" | awk '{print $0}'
P.S. this treats the variable as a file input.
ENVIRON input
As TrueY writes, you can use the ENVIRON to print Environment Variables.
Setting a variable before running AWK, you can print it out like this:
X=MyVar
awk 'BEGIN{print ENVIRON["X"],ENVIRON["SHELL"]}'
MyVar /bin/bash
ARGV input
As Steven Penny writes, you can use ARGV to get the data into awk:
v="my data"
awk 'BEGIN {print ARGV[1]}' "$v"
my data
To get the data into the code itself, not just the BEGIN:
v="my data"
echo "test" | awk 'BEGIN{var=ARGV[1];ARGV[1]=""} {print var, $0}' "$v"
my data test
Variable within the code: USE WITH CAUTION
You can use a variable within the awk code, but it's messy and hard to read, and as Charles Duffy points out, this version may also be a victim of code injection. If someone adds bad stuff to the variable, it will be executed as part of the awk code.
This works by extracting the variable within the code, so it becomes a part of it.
If you want to make an awk that changes dynamically with use of variables, you can do it this way, but DO NOT use it for normal variables.
variable="line one\nline two"
awk 'BEGIN {print "'"$variable"'"}'
line one
line two
Here is an example of code injection:
variable='line one\nline two" ; for (i=1;i<=1000;++i) print i"'
awk 'BEGIN {print "'"$variable"'"}'
line one
line two
1
2
3
.
.
1000
You can add lots of commands to awk this way. Even make it crash with non valid commands.
One valid use of this approach, though, is when you want to pass a symbol to awk to be applied to some input, e.g. a simple calculator:
$ calc() { awk -v x="$1" -v z="$3" 'BEGIN{ print x '"$2"' z }'; }
$ calc 2.7 '+' 3.4
6.1
$ calc 2.7 '*' 3.4
9.18
There is no way to do that using an awk variable populated with the value of a shell variable, you NEED the shell variable to expand to become part of the text of the awk script before awk interprets it. (see comment below by Ed M.)
Extra info:
Use of double quote
It's always good to double quote variable "$variable"
If not, multiple lines will be added as a long single line.
Example:
var="Line one
This is line two"
echo $var
Line one This is line two
echo "$var"
Line one
This is line two
Other errors you can get without double quote:
variable="line one\nline two"
awk -v var=$variable 'BEGIN {print var}'
awk: cmd. line:1: one\nline
awk: cmd. line:1: ^ backslash not last character on line
awk: cmd. line:1: one\nline
awk: cmd. line:1: ^ syntax error
And with single quote, it does not expand the value of the variable:
awk -v var='$variable' 'BEGIN {print var}'
$variable
More info about AWK and variables
Read this faq.
It seems that the good-old ENVIRON awk built-in hash is not mentioned at all. An example of its usage:
$ X=Solaris awk 'BEGIN{print ENVIRON["X"], ENVIRON["TERM"]}'
Solaris rxvt
You could pass in the command-line option -v with a variable name (v) and a value (=) of the environment variable ("${v}"):
% awk -vv="${v}" 'BEGIN { print v }'
123test
Or to make it clearer (with far fewer vs):
% environment_variable=123test
% awk -vawk_variable="${environment_variable}" 'BEGIN { print awk_variable }'
123test
You can utilize ARGV:
v=123test
awk 'BEGIN {print ARGV[1]}' "$v"
Note that if you are going to continue into the body, you will need to adjust
ARGC:
awk 'BEGIN {ARGC--} {print ARGV[2], $0}' file "$v"
I just changed #Jotne's answer for "for loop".
for i in `seq 11 20`; do host myserver-$i | awk -v i="$i" '{print "myserver-"i" " $4}'; done
I had to insert date at the beginning of the lines of a log file and it's done like below:
DATE=$(date +"%Y-%m-%d")
awk '{ print "'"$DATE"'", $0; }' /path_to_log_file/log_file.log
It can be redirect to another file to save
Pro Tip
It could come handy to create a function that handles this so you dont have to type everything every time. Using the selected solution we get...
awk_switch_columns() {
cat < /dev/stdin | awk -v a="$1" -v b="$2" " { t = \$a; \$a = \$b; \$b = t; print; } "
}
And use it as...
echo 'a b c d' | awk_switch_columns 2 4
Output:
a d c b
I have a text files with a line like this in them:
MC exp. sig-250-0 events & $0.98 \pm 0.15$ & $3.57 \pm 0.23$ \\
sig-250-0 is something that can change from file to file (but I always know what it is for each file). There are lines before and above this, but the string "MC exp. sig-250-0 events" is unique in the file.
For a particular file, is there a good way to extract the second number 3.57 in the above example using bash?
use awk for this:
awk '/MC exp. sig-250-0/ {print $10}' your.txt
Note that this will print: $3.57 - with the leading $, if you don't like this, pipe the output to tr:
awk '/MC exp. sig-250-0/ {print $10}' your.txt | tr -d '$'
In comments you wrote that you need to call it in a script like this:
while read p ; do
echo $p,awk '/MC exp. sig-$p/ {print $10}' filename | tr -d '$'
done < grid.txt
Note that you need a sub shell $() for the awk pipe. Like this:
echo "$p",$(awk '/MC exp. sig-$p/ {print $10}' filename | tr -d '$')
If you want to pass a shell variable to the awk pattern use the following syntax:
awk -v p="MC exp. sig-$p" '/p/ {print $10}' a.txt | tr -d '$'
More lines would've been nice but I guess you would like to have a simple use awk.
awk '{print $N}' $file
If you don't tell awk what kind of field-separator it has to use it will use just a space ' '. Now you just have to count how many fields you have got to get your field you want to get. In your case it would be 10.
awk '{print $10}' file.txt
$3.57
Don't want the $?
Pipe your awk result to cut:
awk '{print $10}' foo | cut -d $ -f2
-d will use the $ als field-separator and -f will select the second field.
If you know you always have the same number of fields, then
#!/bin/bash
file=$1
key=$2
while read -ra f; do
if [[ "${f[0]} ${f[1]} ${f[2]} ${f[3]}" == "MC exp. $key events" ]]; then
echo ${f[9]}
fi
done < "$file"
Can any one advise how to search on linux for some data between a tilde character. I need to get IP data however its been formed like the below.
Details:
20110906000418~118.221.246.17~DATA~DATA~DATA
One more:
echo '20110906000418~118.221.246.17~DATA~DATA~DATA' | sed -r 's/[^~]*~([^~]+)~.*/\1/'
echo "20110906000418~118.221.246.17~DATA~DATA~DATA" | cut -d'~' -f2
This uses the cut command with the delimiter set to ~. The -f2 switch then outputs just the 2nd field.
If the text you give is in a file (called filename), try:
grep "[0-9]*~" filename | cut -d'~' -f2
With cut:
echo "20110906000418~118.221.246.17~DATA~DATA~DATA" | cut -d~ -f2
With awk:
echo "20110906000418~118.221.246.17~DATA~DATA~DATA"
| awk -F~ '{ print $2 }'
In awk:
echo '20110906000418~118.221.246.17~DATA~DATA~DATA' | awk -F~ '{print $2}'
Just use bash
$ string="20110906000418~118.221.246.17~DATA~DATA~DATA"
$ echo ${string#*~}
118.221.246.17~DATA~DATA~DATA
$ string=${string#*~}
$ echo ${string%%~*}
118.221.246.17
one more, using perl:
$ perl -F~ -lane 'print $F[1]' <<< '20110906000418~118.221.246.17~DATA~DATA~DATA'
118.221.246.17
bash:
#!/bin/bash
IFS='~'
while read -a array;
do
echo ${array[1]}
done < ip
If string is constant, the following parameter expansion performs substring extraction:
$ a=20110906000418~118.221.246.17~DATA~DATA~DATA
$ echo ${a:15:14}
118.221.246.17
or using regular expressions in bash:
$ echo $(expr "$a" : '[^~]*~\([^~]*\)~.*')
118.221.246.17
last one, again using pure bash methods:
$ tmp=${a#*~}
$ echo $tmp
118.221.246.17~DATA~DATA~DATA
$ echo ${tmp%%~*}
118.221.246.17