I write "if grep a and grep b" structure
if [ grep -q Bug test.txt ] && [ grep -q Ver test.txt ]
then
echo "found"
else
echo "not found"
fi
But the result is wrong, what is the true grammar of the code?
The wrong result:
./test.sh: line 2: [: too many arguments
not found
The condition in a shell if is a command, so
if grep -q Bug test.txt && grep -q Ver test.txt; then
echo "found"
else
echo "not found"
fi
This holds true even for if [ foo -eq bar ]; [ is a command (an alias for test) that returns 0 (which is by convention true in the shell) if the condition it is asked to evaluate is true. grep returns 0 if it finds a match and a non-zero value (by convention false in the shell) otherwise, so if grep -q foo bar is fine.
Related
#!/bin/ksh
if [ -n "$1" ]
then
if grep -w -- "$1" codelist.lst
then
true
else
echo "Value not Found"
fi
else
echo "Please enter a valid input"
fi
This is my script and it works exactly how I want at the moment, I want to add if I add more arguments It will give me the multiple outputs, How can I do that?
So For Example I do ./test.sh apple it will grep apple in codelist.lst and Give me the output : Apple
I want to do ./test.sh apple orange and will do:
Apple
Orange
You can do that with shift and a loop, something like (works in both bash and ksh):
for ((i = $#; i > 0 ; i--)) ; do
echo "Processing '$1'"
shift
done
You'll notice I've also opted not to use the [[ -n "$1" ]] method as that would terminate the loop early with an empty string (such as with ./script.sh a b "" c stopping without doing c).
To iterate over the positional parameters:
for pattern in "$#"; do
grep -w -- "$pattern" codelist.lst || echo "'$pattern' not Found"
done
For a more advanced usage, which only invokes grep once, use the -f option with a shell process substitution:
grep -w -f <(printf '%s\n' "$#") codelist.lst
I have tried all the solutions available on stack overflow, but when I use if condition with with it always results true.
I need to find a line in the file and see if it doesn't exit then insert the line in that file, but it always results that the line already exists.
Here is my script
isInFile=$(grep -q '^export' /etc/bashrc)
if [[ $isInFile == 0 ]];
then
echo "line is not present";
echo "export PROMPT_COMMAND='RETRN_VAL=\$?;logger -p local6.debug \"\$(whoami) [\$\$]: \$(history 1 | sed \"s/^[ ]*[0-9]\+[ ]*//\" )\"'" >> /etc/bashrc;
source /etc/bashrc;
else
echo "line is in the file";
fi
It always says that
line is in the file
The if statement branches based on the exit status of the command it's given. [[ is just one command you can use, it's not mandatory syntax. At an interactive prompt, enter help if
Do this:
if grep -q '^export' /etc/bashrc
then
# exit status of grep is zero: the pattern DOES MATCH the file
echo "line is in the file";
else
# exit status of grep is non-zero: the pattern DOES NOT MATCH the file
echo "line is not present";
echo "export PROMPT_COMMAND='RETRN_VAL=\$?;logger -p local6.debug \"\$(whoami) [\$\$]: \$(history 1 | sed \"s/^[ ]*[0-9]\+[ ]*//\" )\"'" >> /etc/bashrc;
source /etc/bashrc;
fi
I see 2 issues in your code:
if [[ $isInFile == 0 ]]; --If condition should not terminate with ;. Remove that.
The expression you are checking is always an empty string. Try echo $isInFile. What you are checking is output of the command, not its return value. Instead, you should remove -q from your grep expression and check if the output is empty or not.
Following code should work:
isInFile=$(grep '^export' /etc/bashrc)
if [ -z "$isInFile" ]
then
echo "line is not present";
echo "export PROMPT_COMMAND='RETRN_VAL=\$?;logger -p local6.debug \"\$(whoami) [\$\$]: \$(history 1 | sed \"s/^[ ]*[0-9]\+[ ]*//\" )\"'" >> /etc/bashrc;
source /etc/bashrc;
else
echo "line is in the file";
fi
-z check for emptiness of variable.
I want to check if a file contains a specific string or not in bash. I used this script, but it doesn't work:
if [[ 'grep 'SomeString' $File' ]];then
# Some Actions
fi
What's wrong in my code?
if grep -q SomeString "$File"; then
Some Actions # SomeString was found
fi
You don't need [[ ]] here. Just run the command directly. Add -q option when you don't need the string displayed when it was found.
The grep command returns 0 or 1 in the exit code depending on
the result of search. 0 if something was found; 1 otherwise.
$ echo hello | grep hi ; echo $?
1
$ echo hello | grep he ; echo $?
hello
0
$ echo hello | grep -q he ; echo $?
0
You can specify commands as an condition of if. If the command returns 0 in its exitcode that means that the condition is true; otherwise false.
$ if /bin/true; then echo that is true; fi
that is true
$ if /bin/false; then echo that is true; fi
$
As you can see you run here the programs directly. No additional [] or [[]].
In case if you want to check whether file does not contain a specific string, you can do it as follows.
if ! grep -q SomeString "$File"; then
Some Actions # SomeString was not found
fi
In addition to other answers, which told you how to do what you wanted, I try to explain what was wrong (which is what you wanted.
In Bash, if is to be followed with a command. If the exit code of this command is equal to 0, then the then part is executed, else the else part if any is executed.
You can do that with any command as explained in other answers: if /bin/true; then ...; fi
[[ is an internal bash command dedicated to some tests, like file existence, variable comparisons. Similarly [ is an external command (it is located typically in /usr/bin/[) that performs roughly the same tests but needs ] as a final argument, which is why ] must be padded with a space on the left, which is not the case with ]].
Here you needn't [[ nor [.
Another thing is the way you quote things. In bash, there is only one case where pairs of quotes do nest, it is "$(command "argument")". But in 'grep 'SomeString' $File' you have only one word, because 'grep ' is a quoted unit, which is concatenated with SomeString and then again concatenated with ' $File'. The variable $File is not even replaced with its value because of the use of single quotes. The proper way to do that is grep 'SomeString' "$File".
Shortest (correct) version:
grep -q "something" file; [ $? -eq 0 ] && echo "yes" || echo "no"
can be also written as
grep -q "something" file; test $? -eq 0 && echo "yes" || echo "no"
but you dont need to explicitly test it in this case, so the same with:
grep -q "something" file && echo "yes" || echo "no"
##To check for a particular string in a file
cd PATH_TO_YOUR_DIRECTORY #Changing directory to your working directory
File=YOUR_FILENAME
if grep -q STRING_YOU_ARE_CHECKING_FOR "$File"; ##note the space after the string you are searching for
then
echo "Hooray!!It's available"
else
echo "Oops!!Not available"
fi
grep -q [PATTERN] [FILE] && echo $?
The exit status is 0 (true) if the pattern was found; otherwise blankstring.
if grep -q [string] [filename]
then
[whatever action]
fi
Example
if grep -q 'my cat is in a tree' /tmp/cat.txt
then
mkdir cat
fi
In case you want to checkif the string matches the whole line and if it is a fixed string, You can do it this way
grep -Fxq [String] [filePath]
example
searchString="Hello World"
file="./test.log"
if grep -Fxq "$searchString" $file
then
echo "String found in $file"
else
echo "String not found in $file"
fi
From the man file:
-F, --fixed-strings
Interpret PATTERN as a list of fixed strings, separated by newlines, any of
which is to be matched.
(-F is specified by POSIX.)
-x, --line-regexp
Select only those matches that exactly match the whole line. (-x is specified by
POSIX.)
-q, --quiet, --silent
Quiet; do not write anything to standard output. Exit immediately with zero
status if any match is
found, even if an error was detected. Also see the -s or --no-messages
option. (-q is specified by
POSIX.)
Try this:
if [[ $(grep "SomeString" $File) ]] ; then
echo "Found"
else
echo "Not Found"
fi
I done this, seems to work fine
if grep $SearchTerm $FileToSearch; then
echo "$SearchTerm found OK"
else
echo "$SearchTerm not found"
fi
grep -q "something" file
[[ !? -eq 0 ]] && echo "yes" || echo "no"
Say, I call grep "blabla" $file in my shell. How could I know whether grep found "blabla" in $file?
I try ret='grep "blabla" $file', will this work by viewing the value of ret? If yes, is ret integer value or string value or something else?
If you do exactly
ret='grep "blabla" $file'
then ret will contain the string "grep "blabla" $file".
If you do (what you meant)
ret=`grep "blabla" $file`
then ret will contain whatever output grep spit out (the lines that matched "blabla" in $file).
If you just want to know whether grep found any lines that matched "blabla" in $file then you want to check the return code of grep -q blabla "$file" (note that you don't need to quote literal strings when they don't contain special characters and that you should quote variable references).
The variable $? contains the return code of the most recently executed command. So
grep -q blabla "$file"
echo "grep returned: $?"
will echo the return code from grep which will be 0 if any lines were output.
The simplest way to test that and do something about it is, however, not to use $? at all but instead to just embed the grep call in an if statement like this
if grep -q blabla "$file"; then
echo grep found something
else
echo grep found nothing
fi
When you run the command
grep blabla "$file"
Status is saved in the variable $?. 0 is good, greater than 0 is bad. So you
could do
grep -q blabla "$file"
if [ $? = 0 ]
then
echo found
fi
Or save to a variable
grep -q blabla "$file"
ret=$?
if [ $ret = 0 ]
then
echo found
fi
Or just use if with grep directly
if grep -q blabla "$file"
then
echo found
fi
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.
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 $() instead of backticks
Replace grep -c '\$' hello.txt by grep -c '\\$' 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 :)
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.
"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
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