CODEWITHSUNDEEP
linuxshellunixgrep
user2647888
user2647888

Reputation: 721

Grep for a dollar sign within backticks

I have a file like this

File name : hello.txt

{1:ABC}{2:BCD}{3:{108:20140619-2}}{4:
:97A::Hi//12345
:97A::Hi//12345
:93B::Hello//FAMT/00000,
:16S:FIN
-}{5:{CHK:BDG6789}}{S:{ABC:}{DEF:S}{WOM:ONHGRT}}

Now basically i'm checking for the existence of $ symbol and as well as :97A: AND im using the below if statement.

if [ `grep -c '\$' hello.txt` -gt 0 ] && [ `grep -c ":97A:" hello.txt` -gt 1 ]
then
echo "condition satisfied"
else
echo "condition not satisfied"
fi

if i execute this im getting condition satisifed echo statement. But id should be the other way round :( since im putting AND condition. Please help on this.

Upvotes: 1

Views: 421

Answers (5)

Adrian Frühwirth
Adrian Frühwirth

Reputation: 45596

Using awk and reading the file only once:

if awk '/[$]/{d++} /:97A:/{o++} END{exit !(d && o>1)}' hello.txt; then
    echo "condition satisfied"
else
    echo "condition not satisfied"
fi

Upvotes: 1

Deleted User
Deleted User

Reputation: 2541

"i'm checking for the existence of $ symbol"

First condition won't match because there is no "$" sign anywhere in your input, therefore output of first grep is 0. As 0 isn't greater than 0, the result is "false". Consequently, the second clause won't be executed at all. "Condition is not satisfied" because your requirement for "satisfied" is: input contains both "$" AND ":97A:".

For a result whether grep matched any line, you don't need to count number of matches.

if grep -q '\$' file; then ...

is a way to use result of grep in a conditional statement without rube-goldbergismns

Upvotes: 1

timgeb
timgeb

Reputation: 78740

I recommend executing your grep commands in a subshell with the $ syntax, then doing the comparison. In my opinion this is the cleaner way and requires you to be less of an escape artist.

if [ $(grep -c '\$' hello.txt) -gt 0 ] && [ $(grep -c ":97A:" hello.txt) -gt 1 ]
then
echo "condition satisfied"
else
echo "condition not satisfied"
fi

For your hello.txt the output will be:

>> bash test.bash 
condition not satisfied

Since there's no dollar sign in your file 

[ $(grep -c '\$' hello.txt) -gt 0 ]

will test

[ 0 -gt 0 ]

and yield false, while 

[ $(grep -c ':97A' hello.txt) -gt 1 ]

will test

[ 2 -gt 1 ]

and yield true. Finally, false && true will yield false and the second echo statement will be executed.

Upvotes: 1

Tiago Lopo
Tiago Lopo

Reputation: 7959

Replace grep -c '\$' hello.txt by grep -c '\\$' hello.txt Then it will work as desired.

ex:

bash -x test.sh 
++ grep -c '\$' hello.txt
+ '[' 0 -gt 0 ']'
+ echo 'condition not satisfied'
condition not satisfied

PS: bash -x is your friend :)

Upvotes: 1

Pavel
Pavel

Reputation: 7562

I also don't understand what you're asking, but from your code I conclude that you have troubles grepping for the dollar sign. I guess you need to escape the backslash as well if you use backticks:

$ echo 'foo$bar' > dollar.txt
$ echo 'foo_bar' > no_dollar.txt

$ [ `grep -c '\$' dollar.txt` -gt 0 ] && echo 1
1

$ [ `grep -c '\$' no_dollar.txt` -gt 0 ] && echo 1
1

$ [ `grep -c '\\$' dollar.txt` -gt 0 ] && echo 1
1

$ [ `grep -c '\\$' no_dollar.txt` -gt 0 ] && echo 1

$ [ `grep -c '\\$' no_dollar.txt` -gt 0 ] || echo 0
0

alternatively, use $() instead of backticks

Upvotes: 1

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