This question already has answers here:
Bash if statement syntax error [duplicate]
(3 answers)
Closed 9 years ago.
I didnt understand what he error here as iam new to shell scripting. Please help me
./bpr: line 8: syntax error near unexpected token `then'
./bpr: line 8: ` if[$(grep -o BPR $file | wc -l) == 1]; then '
You need to add spaces between your [ ], try this:
if [ $(grep -o BPR $file | wc -l) == 1 ]; then
You need a space around your condition:
if [ $(grep -o BPR $file | wc -l) == 1 ]; then
^ ^
1) If you are using bash, you can use the built-in [[ ..]] instead of test ([ ...]) command.
2) You can also avoid wc by using -c option of grep.
if [[ $(grep -c -o BPR $file) == 1 ]]; then
Aside from your syntax errors, you don't need wc either if you don't care that there may be multiple occurrances of BPR in the file:
if grep -o BPR "$file"; then
A couple of things:
You need spaces around [ and ].
You probably don't want to use [ and ].
The if statement runs the command you give it. If the command returns a zero, the then portion of the if statement is executed. If the command returns a non-zero, the else portion (if it exists) is executed.
Try this:
$ if ls some.file.name.that.does.not.exist
> then
> echo "Hey, the file exists!"
> else
> echo "Nope. File isn't there"
> fi
You'll get an output:
ls: some.file.name.that.does.not.exist: No such file or directory
Nope. File isn't there
That first statement, of course is the output of your ls command. The second one is the output from the if statement. The ls ran, but couldn't access that file (it doesn't exist) and returned e 1. That caused the else clause to execute.
Try this:
$ touch foo
$ if ls foo
> echo "Hey, the file exists!"
> else
> echo "Nope. File isn't there"
> fi
You'll get an output:
foo
Hey, the file exists!
Again the first line is your output from ls. Since the file exists, and is statable, ls returned a 0. This caused the if clause to execute, printing the second line.
What if I want to test whether or not a file exists?
You can use the test command:
$ if test -e foo
> then
> echo "Hey, the file exists!"
> else
> echo "Nope. File isn't there"
> fi
If the file foo exists, the test command returns a 0. That means the echo "Hey, the file exists!" will execute. If the file doesn't exist, test will return a 1, and the else clause will execute.
Now do this:
$ ls -il /bin/test /bin/[
10958 -rwxr-xr-x 2 root wheel 18576 May 28 22:27 /bin/[
10958 -rwxr-xr-x 2 root wheel 18576 May 28 22:27 /bin/test
That first number is the inode. If two matching files have the same inode, they are hard linked to each other. The [... ] are merely another name for the test command. The [ is an actual command. That's why you need spaces around it. You also see that if tests whether or not a command succeeds, and doesn't really do boolean checking (the exception is if you use double square brackets like [[ and ]] instead of [ and ]. These are built into the shell and not as builtin commands.)
What you probably want to do is:
if grep -q "BPR" "$file"
then
echo "'BPR' is in '$file'"
fi
The -q flag tells grep to shut its yap. The grep command will return a 0 if the pattern you give it is in the file, and a non-zero (exact value doesn't matter -- as long as it isn't 0) if it can't.
Note I don't need [ ... ] because I am using the output of the grep command to see if I should execute the if clause of that statement.
if you only need to know if the string matches without showing the actual match use
if grep -q 'anystring' file ; then
Related
I have the following list:
COX1
COX1
COX1
COX1
COX1
Cu-oxidase
Cu-oxidase_3
Cu-oxidase_3
Fer4_NifH
and I want to search if COX1 and Cu-oxidase is in the list, I want to print xyz, if Cu-oxidase_3 and Fer4_NifHis in the list too (independent if the first two are in the list, then it should print abc.
This is what I could script so far:
if grep 'COX1' file.txt; then echo xyz; else exit 0; fi
but it is of course incomplete.
Any solution to that?
ideally my output would be:
xyz
abc
Awk lets you easily search for multiple regular expressions and print something else than the matched string itself. (grep can easily search for multiple patterns, too, but it will print the match or its line number or file name, not some arbitrary string.)
The following assumes that you have a single token per line. This assumption makes the script really simple, though it would also not be hard to support other scenarios.
awk '{ a[$1]++ }
END { if (("COX1" in a) && ("Cu-oxidase" in a)) print "xyz";
if (("Cu-oxidase_3" in a) && ("Fer4_NifH" in a)) print "abc" }' file.txt
This builds an associative array of each token (actually the first whitespace-separated token on each line) and then at the end, when it has read every line in the file, checks whether the sought tokens exist as keys in the array.
Performing a single pass over the input file is a big win especially if you have a large input file and many patterns. Just for completeness, the syntax for performing multiple passes with grep is very straightforward;
if grep -qx 'COX1' file.txt && grep -qx 'Cu-oxidase' file.txt
then
echo xyz
fi
which can be further abbreviated to
grep -qx 'COX1' file.txt && grep -qx 'Cu-oxidase' file.txt && echo xyz
Notice the -x switch to require the whole line to match (otherwise the regex 'Cu-oxidase' would also match on the Cu-oxidase_3 lines).
Above is a very verbose way to achieve this. There are ways to write the same with less ifs and less greps, but I really wanted to show you the logic:
you run a grep command, check for its return value with $?, and finally acts on the conditions.
# default values
HAS_COX1=0
HAS_CUOX=0
HAS_CUO3=0
HAS_FER4=0
# run silently grep
grep -q 'COX1' file.txt
# check for return value and set variable accordingly
if [ $? -eq 0 ]; then HAS_COX1=1; fi
# same as above
grep -q 'Cu-oxidase' file.txt
if [ $? -eq 0 ]; then HAS_CUOX=1; fi
grep -q 'Cu-oxidase_3' file.txt
if [ $? -eq 0 ]; then HAS_CUO3=1; fi
grep -q 'Fer4_NifH' file.txt
if [ $? -eq 0 ]; then HAS_FER4=1; fi
if [ $HAS_COX1 -eq 1 ]; then
if [ $HAS_CUOX -eq 1 ]; then
echo 'xyz'
exit 0
fi
fi
if [ $HAS_CUO3 -eq 1 ]; then
if [ $HAS_FER4 -eq 1 ]; then
echo 'abc'
exit 0
fi
fi
echo 'None of the checks where matched'
exit 1
Beware: this code is untested, so there might be bugs ☺
The code isn't perfect, as it cannot print both 'xyz' and 'abc' when both conditions are met (but that would be an easy fix with the syntax I provide). Also $HAS_CUOX will be set to 1 whenever $HAS_CUO3 is found (no boundary checking in the grep regex).
You could take that code further by using a single grep for each set of conditions to check, using something like 'COX1\|Cu_oxidase' as the regex for grep. And also fix the minor issues I mentioned above.
ideally my output would be:
xyz
abc
You added your expected output after I wrote the above script, but given the elements I gave you, you should be able to figure how to improve that (basically removing the exit 0 where I placed them, and doing exit 1 when no output has been given.
Or just remove all exits as a dirty solution.
I am learning bash. I would like to get the return value and matched line by grep at once.
if cat 'file' | grep 'match_word'; then
match_by_grep="$(cat 'file' | grep 'match_word')"
read a b <<< "${match_by_grep}"
fi
In the code above, I used grep twice. I cannot think of how to do it by grep once. I am not sure match_by_grep is always empty even when there is no matched words because cat may output error message.
match_by_grep="$(cat 'file' | grep 'match_word')"
if [[ -n ${match_by_grep} ]]; then
# match_by_grep may be an error message by cat.
# So following a and b may have wrong value.
read a b <<< "${match_by_grep}"
fi
Please tell me how to do it. Thank you very much.
You can avoid the double use of grep by storing the search output in a variable and seeing if it is not empty.
Your version of the script without double grep.
#!/bin/bash
grepOutput="$(grep 'match_word' file)"
if [ ! -z "$grepOutput" ]; then
read a b <<< "${grepOutput}"
fi
An optimization over the above script ( you can remove the temporary variable too)
#!/bin/bash
grepOutput="$(grep 'match_word' file)"
[[ ! -z "$grepOutput" ]] && (read a b <<< "${grepOutput}")
Using double-grep once for checking if-condition and once to parse the search result would be something like:-
#!/bin/bash
if grep -q 'match_word' file; then
grepOutput="$(grep 'match_word' file)"
read a b <<< "${grepOutput}"
fi
When assigning a variable with a string containing a command expansion, the return code is that of the (rightmost) command being expanded.
In other words, you can just use the assignment as the condition:
if grepOutput="$(cat 'file' | grep 'match_word')"
then
echo "There was a match"
read -r a b <<< "${grepOutput}"
(etc)
else
echo "No match"
fi
Is this what you want to achieve?
grep 'match_word' file ; echo $?
$? has a return value of the command run immediately before.
If you would like to keep track of the return value, it will be also useful to have PS1 set up with $?.
Ref: Bash Prompt with Last Exit Code
I'd like to add an argument to a command in bash only if a variable evaluates to a certain value. For example this works:
test=1
if [ "${test}" == 1 ]; then
ls -la -R
else
ls -R
fi
The problem with this approach is that I have to duplicate ls -R both when test is 1 or if it's something else. I'd prefer if I could write this in one line instead such as this (pseudo code that doesn't work):
ls (if ${test} == 1 then -la) -R
I've tried the following but it doesn't work:
test=1
ls `if [ $test -eq 1 ]; then -la; fi` -R
This gives me the following error:
./test.sh: line 3: -la: command not found
A more idiomatic version of svlasov's answer:
ls $( (( test == 1 )) && printf %s '-la' ) -R
Since echo understands a few options itself, it's safer to use printf %s to make sure that the text to print is not mistaken for an option.
Note that the command substitution must not be quoted here - which is fine in the case at hand, but calls for a more robust approach in general - see below.
However, in general, the more robust approach is to build up arguments in an array and pass it as a whole:
# Build up array of arguments...
args=()
(( test == 1 )) && args+=( '-la' )
args+=( '-R' )
# ... and pass it to `ls`.
ls "${args[#]}"
Update: The OP asks how to conditionally add an additional, variable-based argument to yield ls -R -la "$PWD".
In that case, the array approach is a must: each argument must become its own array element, which is crucial for supporting arguments that may have embedded whitespace:
(( test == 1 )) && args+= ( '-la' "$PWD" ) # Add each argument as its own array element.
As for why your command,
ls `if [ $test -eq 1 ]; then -la; fi` -R
didn't work:
A command between backticks (or its modern, nestable equivalent, $(...)) - a so-called command substitution - is executed just like any other shell command (albeit in a sub-shell) and the whole construct is replaced with the command's stdout output.
Thus, your command tries to execute the string -la, which fails. To send it to stdout, as is needed here, you must use a command such as echo or printf.
Print the argument with echo:
test=1
ls `if [ $test -eq 1 ]; then echo "-la"; fi` -R
I can't say how acceptable this is, but:
test=1
ls ${test:+'-la'} -R
See https://stackoverflow.com/revisions/16753536/1 for a conditional truth table.
Another answer without using eval and using BASH arrays:
myls() { local arr=(ls); [[ $1 -eq 1 ]] && arr+=(-la); arr+=(-R); "${arr[#]}"; }
Use it as:
myls
myls "$test"
This script builds whole command in an array arr and preserves the original order of command options.
I wrote a bash script that uploads a file on my home server. It gets activated from a folder action script using applescript. The setup is the folder on my desktop is called place_on_server. Its supposed to have an internal file structure exactly like the folder I want to write to: /var/www/media/
usage goes something like this:
if directory etc added to place_on_server: ./upload DIR etc
if directory of directory: etc/movies ./upload DIR etc movies //and so on
if file to place_on_server: ./upload F file.txt
if file in file in place_on_server ./upload F etc file.txt //and so on
for creating a directory its supposed to execute a command like:
ssh root#192.168.1.1<<EOF
cd /var/www/media/wherever
mkdir newdirectory
EOF
and for file placement:
rsync -rsh='ssh -p22' file root#192.168.1.1:/var/www/media/wherever
script:
#!/bin/bash
addr=$(ifconfig -a | ./test)
if ($# -le "1")
then
exit
elif ($1 -eq "DIR")
then
f1="ssh -b root#$addr<<EOF"
list = "cd /var/www/media\n"
if($# -eq "2")
then
list=list+"mkdir $2\nEOF\n"
else
num=2
i=$(($num))
while($num < $#)
do
i=$(($num))
list=list+"mkdir $i\n"
list=list+"cd $i\n"
$num=$num+1
done
fi
echo $list
elif ($1 -eq "F")
then
#list = "cd /var/www/media\n"
f2="rsync -rsh=\'ssh -p22\' "
f3 = "root#$addr:/var/www/media"
if($# -eq "2")
then
f2=f2+$2+" "+f3
else
num=3
i=$(($num))
while($num < $#)
do
i=$(($num))
f2=f2+"/"+$i
$num=$num+1
done
i=$(($num))
f2=f2+$i+" "+$f3
fi
echo $f2
fi
exit
output:
(prompt)$ ./upload2 F SO test.txt
./upload2: line 3: 3: command not found
./upload2: line 6: F: command not found
./upload2: line 25: F: command not found
So as you can see I'm having issues handling input. Its been awhile since I've done bash. And it was never extensive to begin with. Looking for a solution to my problem but also suggestions. Thanks in advance.
For comparisons, use [[ .. ]]. ( .. ) is for running commands in subshells
Don't use -eq for string comparisons, use =.
Don't use < for numerical comparisons, use -lt
To append values, f2="$f2$i $f3"
To add line feeds, use $'\n' outside of double quotes, or a literal linefeed inside of them.
You always need "$" on variables in strings to reference them, otherwise you get the literal string.
You can't use spaces around the = in assignments
You can't use $ before the variable name in assignments
To do arithmetics, use $((..)): result=$((var1+var2))
For indirect reference, such as getting $4 for n=4, use ${!n}
To prevent word splitting removing your line feeds, double quote variables such as in echo "$line"
Consider writing smaller programs and checking that they work before building out.
Here is how I would have written your script (slightly lacking in parameter checking):
#!/bin/bash
addr=$(ifconfig -a | ./test)
if [[ $1 = "DIR" ]]
then
shift
( IFS=/; echo ssh "root#$addr" mkdir -p "/var/www/media/$*"; )
elif [[ $1 = "F" ]]
then
shift
last=$#
file=${!last}
( IFS=/; echo rsync "$file" "root#$addr:/var/www/media/$*" )
else
echo "Unknown command '$1'"
fi
$* gives you all parameters separated by the first character in $IFS, and I used that to build the paths. Here's the output:
$ ./scriptname DIR a b c d
ssh root#somehost mkdir -p /var/www/media/a/b/c/d
$ ./scriptname F a b c d somefile.txt
rsync somefile.txt root#somehost:/var/www/media/a/b/c/d/somefile.txt
Remove the echos to actually execute.
The main problem with your script are the conditional statements, such as
if ($# -le "1")
Despite what this would do in other languages, in Bash this is essentially saying, execute the command line $# -le "1" in a subshell, and use its exit status as condition.
in your case, that expands to 3 -le "1", but the command 3 does not exist, which causes the error message
./upload2: line 3: 3: command not found
The closest valid syntax would be
if [ $# -le 1 ]
That is the main problem, there are other problems detailed and addressed in that other guy's post.
One last thing, when you're assigning value to a variable, e.g.
f3 = "root#$addr:/var/www/media"
don't leave space around the =. The statement above would be interpreted as "run command f3 with = and "root#$addr:/var/www/media" as arguments".
I have the following korn script:
#!/bin/ksh
TAPPDATADIR=/hp/qa02/App/IPHSLDI/Data
echo $TAPPDATADIR
if [[ls $TAPPDATADIR/zip_file_MD5_checksum*.txt | wc -l > 1]]
then
exit "asdf"
fi
When I attempt to run it I get:
/hp/qa02/App/IPHSLDI/Data
./iftest.ksh: line 7: [[ls: not found
Why isn't my if statement working?
I'm trying to see if there are multiple checksum files in the Data directory. If there are I want to exit the script.
There are several problems:
There shouldn't be any spaces around = in the assignment.
You need spaces around [[ and ]] in the if statement.
To substitute the result of a command into the test expression, you need to use backticks or $(...).
The parameter to exit should be a number, I think you just want to echo the string.
> performs string comparison, you have to use -gt to perform numeric comparison.
So the full script should be:
#!/bin/ksh
TAPPDATADIR=/hp/qa02/App/IPHSLDI/Data
echo $TAPPDATADIR
if [[ $(ls $TAPPDATADIR/zip_file_MD5_checksum*.txt | wc -l) -gt 1 ]]
then
echo "asdf"
fi