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question on sed grep awk from variable

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# 1  
Old 08-10-2006
question on sed grep awk from variable
i am still confusing on how to use sed, grep and awk if the input is not a file but a variable.

such as:

a="hello world"
b="how are you"
c="best wish to you"
d="222,333,444"

what if i want to check which variable $a,$b,$c,$d have contain "you"
what if i want to replace the word "you" to "me"
what if i want to grep the 2nd field of the varible

How should i do ?
Does echo $* must be use in all case ?
Can someone give me a good example on this ?

Many thanks !!
# 2  
Old 08-10-2006
To use sed(or awk or grep) on a variable :
Code:
echo $variable | sed ....

To check wich variable contains 'you'
Code:
a="hello world"
b="how are you"
c="best wish to you"
d="222,333,444"

# check if variable 'a' contains 'you'

if echo "$a" | grep -q you
then
   echo "Variable a contains 'you'"
fi

# Print variables values which contains 'you'

cat <<EOD | awk -v FS='=' '/you/'
$a
$b
$c
$d
EOD

# Print variables names of variables which contains 'you'

cat <<EOD | awk -v FS='=' '/you/ {print $1}'
a=$a
b=$b
c=$c
d=$d
EOD

To replace the word "you" to "me" :
Code:
a="hello world"
b="how are you"
c="best wish to you"
d="222,333,444"

# Replace 'you' by 'me' in variable b

b=$(echo "$b" | sed 's/you/me/')

# Replace 'you' by 'me' in variablesa b c d

b="how are you"
for var in a b c d
do
   eval value="\$$var"
   new_value=$(echo "$value" | sed 's/you/me/' )
   eval $var="\$new_value"
   # Can be done in one statement :
   # eval $var=\$\(echo "\$$var" \| sed 's/you/me/' \)
done

To grep the 2nd field of the variable
Code:
d="222,333,444"

# grep field 2 of variable d (seperator=,)

field2=$(echo "$d" | cut -d, -f2)


Jean-Pierre.
# 3  
Old 08-11-2006
# check if variable 'a' contains 'you'

if echo "$a" | grep -q you
then
echo "Variable a contains 'you'"
fi

I have the following output ---->
egrep: illegal option -- q
usage: egrep [ -bchilnsv ] [ -e exp ] [ -f file ] [ strings ] [ file ] ...


Also, i have one more question:
how to pass the variable out of awk?
example of my script but did not work.

echo $* | awk -F: '{a=$1 b=$2 c=$3}'
#echo $* | awk -F: '{"a=%s b=%s c=%s\n",$1, $2, $3}' <<- not work too.
print $a
print $b
print $c


thanks you!
# 4  
Old 08-11-2006
  1. grep != egrep
  2. eval `echo $* | awk -F: '{printf("a=%s; b=%s; c=%s\n", $1, $2, $3)}'`
    print $a
    print $b
    print $c
# 5  
Old 08-11-2006
Why would you want to test $a like that?

if [[ $a = *you* ]]
then
...
fi
Last edited by tmarikle; 08-11-2006 at 12:44 AM.. Reason: Duplicate answers...again
# 6  
Old 08-11-2006
thanks you
Quote:
Originally Posted by vgersh99
  1. grep != egrep
  2. eval `echo $* | awk -F: '{printf("a=%s; b=%s; c=%s\n", $1, $2, $3)}'`
    print $a
    print $b
    print $c
oh.. both grep and egrep not work too

grep: illegal option -- q
Usage: grep -hblcnsviw pattern file . . .
# 7  
Old 08-11-2006
what OS are you on?
If on Solaris try '/usr/xpg4/bin/grep'
or try tmarikle's suggestion - much better approach
Last edited by vgersh99; 08-11-2006 at 01:14 AM..
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