I am trying to assign output of a cut command to a variable, however I am running into a strange problem.
I am using tcsh shell.
$echo $0
tcsh
This is the command I am running:
$set a=`cut -f2 -d' ' test.txt`
Missing }. //This is the output I am getting
Now the file is real simple (well this is the not the file I was working on but I reduced the problem to this.)
Test.txt:
{ {corner
Thats it! This is the file. If I change the file to this:
{ {corner}
Statement works but "a" gets the following value:
$echo $a
corner //Please note its not {corner} but corner
Hence I think that shell is trying to execute {corner
as a command and since its missing the closing brace shell complains. Does anyone have any idea why its showing this behavior? My understanding is that it should just assign the output of cut to the variable but looks like its assigning it recursively!
Newbie
You have to wrap it around double quotes
set a="`cut -f2 -d' ' test.txt`"
Same applies to uses such as echo
echo "$a"
Output
{corner
Related
So I am trying to make a script that contains egrep and accepts a numeric variable
#!/bin/bash
var=$1
list="egrep "^.{$var}$ /usr/share/dict/words"
cat list
For example, if var is 5, I would like this script to print out every line with 5 characters. For some reason the script does not do that. Help would be greatly appreciated!
Your script doesn't work because there are several problems with these lines:
list="egrep "^.{$var}$ /usr/share/dict/words"
cat list
The first line isn't complete, it's missing a closing quote,
Even if you fixed it, you're assigning a literal string to list, not the output of a command,
RE and filename should be separated
cat doesn't print a variable's content, echo does that.
So:
#!/bin/bash
var="$1"
list="$(egrep '^.{'"$var"'}$' /usr/share/dict/words)"
echo "$list"
should work.
Or even better, you can use just an awk command:
awk 'length==5' /usr/share/dict/words
with $1 or any other variable:
awk -v n="$1" 'length==n' /usr/share/dict/words
I know this seems fairly trivial. But I have no idea where I am going wrong. I have a shell script where I download a package based on the input argument and then extract the package name. This is how I do it:
wget $1
echo $1 | awk -F/ '{print $NF}'
I run it like this bash scrip.sh http://apache.claz.org/phoenix/apache-phoenix-4.10.0-HBase-1.2/bin/apache-phoenix-4.10.0-HBase-1.2-bin.tar.gz
I download the package and then the second line splits the input variable along the / delimiter I get apache-phoenix-4.10.0-HBase-1.2-bin.tar.gz. Now I want to assign the result of the second line to a variable. I change my script to a dir=$($1 | awk -F/ '{print $NF}') and add an echo $dir to the script to see the result. However I keep running into this error : line 2: http://apache.claz.org/phoenix/apache-phoenix-4.10.0-HBase-1.2/bin/apache-phoenix-4.10.0-HBase-1.2-bin.tar.gz: No such file or directory
I tried wrapping the command into `` but the problem persists. I am not cd-ing into any directory so I have no idea why this error keeps showing up.
I have a wierd situation. I am trying to cut some info from a file and everything works fine when I run the command straight into the terminal, but as soon as I make it a variable in a script it returns a mixture of what it should cut and a list of the files in the current directory.
cat query.sql | cut -d':' -f3,4
works but...
QUERY_SQL="query.sql"
MYSQL_COMMAND=`cat $QUERY_SQL | cut -d':' -f3,4`
echo $MYSQL_COMMAND
returns the wierd output mentioned above.
What am I doing wrong?
EDIT:
The query file looks something like this...
email#somehwhere.com:3:SQL CODE
I suspect something in the contents of MYSQL_COMMAND is being interpreted as a filename glob pattern. Try changing
MYSQL_COMMAND=`cat $QUERY_SQL | cut -d':' -f3,4`
echo $MYSQL_COMMAND
to
MYSQL_COMMAND="$(cut -d: -f3,4 < "$QUERY_SQL")"
printf '%s\n' "$MYSQL_COMMAND"
Best defensive coding practice for shell is to put double quotes around every variable substitution, unless you know for a fact that you need word splitting and glob expansion to happen after a particular substitution. Changing echo to printf '%s\n' avoids a related set of problems. I can never remember whether you actually need double quotes around $(...) in a variable assignment, so I put them in just to be safe.
I have the following line at the first line in my script file:
#!/bin/sh
So I'm using csh.(?)
I wanto assign the output of the following to an environment variable:
echo $MYUSR | awk '{print substr($0,4)}'
I try:
set $MYVAR = echo $MYUSR | awk '{print substr($0,4)}'
But it doesn't work,
How can I do it? I want to do it in a sh file.
Your script should look like
#!/bin/csh
set MYVAR = `echo $MYUSR | awk '{print substr($0,4)}'`
echo $MYVAR
I don't have a way to test this right now, let me now if it doesn't work.
If you've inherited the basis of your script from someone else, with the #!/bin/sh,
then you have to find out if /bin/sh is really the bourne shell, or if it is a link to /bin/bash
You can tell that by doing
ls -l /bin/sh /bin/bash
if you get back information on files where the size is exactly the same, the you're really using bash, but called as /bin/sh
So try these 2 solutions
MYVAR=$(echo $MYUSR | awk '{print substr($0,4)}')
echo $MYVAR
AND
MYVAR=``echo $MYUSR | awk '{print substr($0,4)}``
echo $MYVAR
# arg!! only one pair of enclosing back-ticks needed,
# can't find the secret escape codes to make this look exactly right.
in all cases (csh) included, the back-ticks AND the $( ... ) are known as command substitution.
What every output comes from running the command inside, is substituted into the command line AND then the whole command is executed.
I hope this helps.
if it's /bin/sh it's bourne shell or bash, and use back quotes to execute something and this to assign that...
MYVAR=`echo $MYUSR | awk ...`
That script first line indicates that it should be interpreted by the Bourne shell (sh), not csh. Change it to
#!/bin/csh
The first line of your code shows clearly you are not using a csh. You are using a plain sh environment/shell. You have 2 options:
Either change the first line to #!/bin/csh OR
Keeping first line unchanged, update the code for setting the variable.
MYVAR=`echo $MYUSR | awk '{print substr($0,4)}`
echo $MYVAR
Let me know, if you get any error.
Beyond Compare provides "Select for compare" and "Compare to Selected" by using two nautilus scripts (stored in /home/user/.gnome2/nautilus-scripts).
Script 1: Select for compare
#!/bin/sh
quoted=$(echo "$NAUTILUS_SCRIPT_SELECTED_FILE_PATHS" | awk 'BEGIN { FS = "\n" } { printf "\"%s\" ", $1 }' | sed -e s#\"\"##)
echo "$quoted" > $HOME/.beyondcompare/nautilus
Script 2: Compare to Selected
#!/bin/sh
arg2=$(cat $HOME/.beyondcompare/nautilus)
arg1=$(echo "$NAUTILUS_SCRIPT_SELECTED_FILE_PATHS" | awk 'BEGIN { FS = "\n" } { printf "\"%s\" ", $1 }' | sed -e s#\"\"##)
bcompare $arg1 $arg2
I am trying to do similar scripts for Meld, but it is not working.
I am not familiar with shell scripts. Can anyone help me understand this:
quoted=$(echo "$NAUTILUS_SCRIPT_SELECTED_FILE_PATHS" | awk 'BEGIN { FS = "\n" } { printf "\"%s\" ", $1 }' | sed -e s#\"\"##)
so that I can adapt to meld.
If you are not rolling your own solution for the sake of learning, I would suggest installing the diff-ext extension to nautilus. It is cross platform and if you are running Debian/Ubuntu installing it should be as simple as sudo apt-get install diff-ext.
Check out some screenshots here - http://diff-ext.sourceforge.net/screenshots.shtml
The quoted=$( ...) assigns whatever output there is to the variable named quoted, and can be used later in the script as $quoted OR ${quoted} OR "${quoted}" OR "$quoted"
The '|' char is called a 'pipe' in unix/linux and it connects the output of the preceding command to feed into the following command.
So you just take the script apart 1 piece at a time and see what it does,
quoted=$(
# I would execute below by itself first
echo "$NAUTILUS_SCRIPT_SELECTED_FILE_PATHS"
# then add on this piped program to see how data gets transformed
| awk 'BEGIN { FS = "\n" } { printf "\"%s\" ", $1 }'
# then add this
| sed -e s#\"\"##
# the capturing of the output to the var 'quoted' is the final step of code
)
# you **cannot** copy paste this whole block of code and expect it to work ;-)
I don't know what is supposed to be in $NAUTILUS_SCRIPT_SELECTED_FILE_PATHS, so it is hard to show you here. AND, that variable is not defined in any of the code you specify here, so you may only get a blank line when you echo its value. Be prepared to do some research on how that value get set AND what are the correct values.
Also I notice that your code is 'prefixed' as #!/bin/sh. If it is truly /bin/sh then command substitution like quoted=$(....) will not work and should generate an error message. Persumably your system is really using bash for /bin/sh. You can eliminate any possible confusion in the future (when changing to a system where /bin/sh = bourne shell), by changing the 'shebang' to #! /bin/bash.
I hope this helps.
I just discovered diff-ext thanks to this post, excellent!
The first try I did failed: by default diff-ext does not handle backup files (*~ and *.bak). To enable this, run:
$ diff-ext-setup
and in the Mime types pane, check application/x-trash.
Now you can compare a file and its backup.