Alright, I have a script that takes a few arguments, runs data, and then rsyncs the data out to a different server. The problem is that to run the data, I have to take one of the arguments and then run a report using it, which is very bash unfriendly (Ex. [3023.2<>1], [5111.3$]="5", etc).
So if I'm going to run the command, I need to put the argument in single quotes, which would then make the argument not be pulled into it.
Thus if I were to run the script...
arg1 = [5111.3$]="5"
runjob specfile.spx '$arg1'
This wouldn't work, but if I were to run it with double quotes, then there is a good chance that the argument that gets passed in will have double quotes. Any ideas on how to get around this?
Use single quotes around the value when you set it, then use double-quotes around the variable when you expand it:
$ arg1='[5111.3$]="5"'
$ echo "$arg1"
[5111.3$]="5"
Quote escapes. Try
[5111.3$]=\"5\"
The Advanced Scripting Guide has a good section on quoting.
Related
I am trying to give an argument to my python program through the terminal.
For this I am using the lines:
import sys
something = sys.argv[1]
I now try to put in a string like this through the bash terminal:
python my_script.py 2m+{N7HiwH3[>!"4y?t9*y#;/$Ar3wF9+k$[3hK/WA=aMzF°L0PaZTM]t*P|I_AKAqIb0O4# cm=sl)WWYwEg10DDv%k/"c{LrS)oVd§4>8bs:;9u$ *W_SGk3CXe7hZMm$nXyhAuHDi-q+ug5+%ioou.,IhC]-_O§V]^,2q:VBVyTTD6'aNw9:oan(s2SzV
This returns a bash error because some of the characters in the string are bash special characters.
How can I use the string exactly as it is?
You can put the raw string into a file, for example like this, with cat and a here document.
cat <<'EOF' > file.txt
2m+{N7HiwH3[>!"4y?t9*y#;/$Ar3wF9+k$[3hK/WA=aMzF°L0PaZTM]t*P|I_AKAqIb0O4# cm=sl)WWYwEg10DDv%k/"c{LrS)oVd§4>8bs:;9u$ *W_SGk3CXe7hZMm$nXyhAuHDi-q+ug5+%ioou.,IhC]-_O§V]^,2q:VBVyTTD6'aNw9:oan(s2SzV
EOF
and then run
python my_script.py "$(< file.txt)"
You can also use the text editor of your choice for the first step if you prefer that.
If this is a reoccurring task, which you have to perform from time to time, you can make your life easier with a little alias in your shell:
alias escape='read -r string ; printf "Copy this:\n%q\n" "${string}"'
It is using printf "%q" to escape your input string.
Run it like this:
escape
2m+{N7HiwH3[>!"4y?t9*y#;/$Ar3wF9+k$[3hK/WA=aMzF°L0PaZTM]t*P|I_AKAqIb0O4# cm=sl)WWYwEg10DDv%k/"c{LrS)oVd§4>8bs:;9u$ *W_SGk3CXe7hZMm$nXyhAuHDi-q+ug5+%ioou.,IhC]-_O§V]^,2q:VBVyTTD6'aNw9:oan(s2SzV
Copy this:
2m+\{N7HiwH3\[\>\!\"4y\?t9\*y#\;/\$Ar3wF9+k\$\[3hK/WA=aMzF°L0PaZTM\]t\*P\|I_AKAqIb0O4#\ cm=sl\)WWYwEg10DDv%k/\"c\{LrS\)oVd§4\>8bs:\;9u\$\ \*W_SGk3CXe7hZMm\$nXyhAuHDi-q+ug5+%ioou.\,IhC\]-_O§V\]\^\,2q:VBVyTTD6\'aNw9:oan\(s2SzV
You can use the escaped string directly in your shell, without additional quotes, like this:
python my_script.py 2m+\{N7HiwH3\[\>\!\"4y\?t9\*y#\;/\$Ar3wF9+k\$\[3hK/WA=aMzF°L0PaZTM\]t\*P\|I_AKAqIb0O4#\ cm=sl\)WWYwEg10DDv%k/\"c\{LrS\)oVd§4\>8bs:\;9u\$\ \*W_SGk3CXe7hZMm\$nXyhAuHDi-q+ug5+%ioou.\,IhC\]-_O§V\]\^\,2q:VBVyTTD6\'aNw9:oan\(s2SzV
In order to make life easier, shells like bash do a little bit of extra work to help users pass the correct arguments to the programs they instruct it to execute. This extra work usually results in predictable argument arrays getting passed to programs.
Oftentimes, though, this extra help results in unexpected arguments getting passed to programs; and sometimes results in the execution of undesired additional commands. In this case, though, it ended up causing Bash to emit an error.
In order to turn off this extra work, Bash allows users to indicate where arguments should begin and end by surrounding them by quotation marks. Bash supports both single quotes (') and double quotes (") to delimit arguments. As a last resort, if a string may contain single and double quotes (or double quotes are required but aren't aggressive enough), Bash allows you to indicate that a special- or whitespace-character should be part of the adjacent argument by preceding it with a backslash (\\).
If this method of escaping arguments is too cumbersome, it may be worth simplifying your program's interface by having it consume this data from a file instead of a command line argument. Another option is to create a program that loads the arguments from a more controlled location (like a file) and directly execs the target program with the desired argument array.
I am trying to study both bash and ruby and I am trying to pass a variable that contains a JSON object from ruby to be printed using a bash script.
I tried storing the JSON object in a variable then used that variable as an argument for my bash script but I am not getting the result that I wanted.
so in my ruby code I have this:
param = request.body
cmd = "ruby_to_bash #{param}"
exec cmd
and in my bash script, I am simply outputting the value of the argument:
echo $1
For example I have this JSON:
{"first":"one","second":"two","third":"three"}
my code only gives me this output:
{first:
I want to display the whole JSON object. How can I do this? Any kind of help will be much appreciated.
Both bash and ruby treat double quotes in a kinda special way: double-quoted strings are interpolated before passed to the receiver. I strongly encourage you to start with learning somewhat one in the first place instead of doing zero progress in both due to induced errors.
Answering the question stated, one must escape double quotes when passing back and forth since both ruby and bash treat them as content delimiters and discard when the content is already parsed in the resulting string.
This would work:
exec %|ruby_to_bash #{param.gsub('"', '\"')}|
I use %| and | as string delimiters to avoid clashes against inner quotes.
Sidenote: the above won’t work for the input containing spaces, but I purposely avoid to show how to deal with spaces since it leads to the dead end; once handled spaces with surrounding the interpolated param with single quotes, we are prone to be screwed up with inner single quotes in JSON object and so forth.
The code above is not someone should ever produce in production.
I think your best bet is, as usual in such cases, not to involve a shell at all.
When you say this:
cmd = "ruby_to_bash #{param}"
exec cmd
Your exec call is invoking a shell which parses cmd and then runs ruby_to_bash so you're doing this:
Build a command line.
Replace the current process with /bin/sh.
/bin/sh parses the command line that you should mashed together. This is where you need to worry about quoting and escaping to get past the shell.
/bin/sh exec's ruby_to_bash.
You could bypass the whole problem by using the multi-argument form of Kernel#exec:
exec(cmdname, arg1, ...)
command name and one or more arguments (no shell)
which doesn't bother with a shell at all. If you say:
exec 'ruby_to_bash', param
You won't involve a shell and the quotes or spacing in param won't matter to anyone other than ruby_to_bash.
I ham having difficulty understanding how to pass a variable to a ./configure command that includes variable expansion and quotes.
myvars.cfg
myFolderA="/home/myPrefix"
myFolderB="/home/stuffB"
myFolderC="/home/stuffC"
optsA="--prefix=${myFolderA}"
optsB="CPPFLAGS=\"-I${myFolderB} -I${myFolderC}\""
cmd="/home/prog/"
myScript.sh
#!/bin/bash
. /home/myvars.cfg
doCmd=("$cmd/configure" "${optsA}" "${optsB}")
${doCmd[#]}
The doCmd should look like this
/home/prog/configure --prefix=/home/myPrefix CPPFLAGS="-I/home/stuffB -I/home/stuffC"
however it seems when running bash it is adding single quotes
/home/prog/configure --prefix=/home/myPrefix 'CPPFLAGS="-I/home/stuffB' '-I/home/stuffC"'
causing an error of
configure: error: unrecognized option: `-I/home/stuffC"'
Is there a way to pass a variable that needs top be expanded and contains double quotes?
As your script is written, there is no point to using the doCmd array. You could simply write the command:
"$cmd/configure" "${optsA}" "${optsB}"
Or, more simply:
"$cmd/configure" "$optsA" "$optsB"
However, it is possible that you've simplified the script in a way which hides the need for the array. In any case, if you use the array, you need to ensure that its elements are not word-split and filepath expanded, so you must quote its expansion:
"${doCmd[#]}"
Also, you need to get rid of the quotes in optsB. You don't want to pass
CPPFLAGS="-I/home/stuffB -I/home/stuffC"
to the configure script. You want to pass what the shell would pass if you typed the above string. And what the shell would pass would be a single command-line argument with a space in it, looking like this:
CPPFLAGS=-I/home/stuffB -I/home/stuffC
In order to get that into optsB, you just write:
optsB="CPPFLAGS=-I${myFolderB} -I${myFolderC}"
Finally, the shell is not "adding single quotes" into the command line. It is showing you a form of the command whch you could type at the command-line. Since the argument (incorrectly) contains a quote symbol, the shell shows you the command with its arguments skingle-quoted, so that you can see that the optB has been (incorrectly) split into two arguments, each of which contains (incorrectly) one double quote.
You could have found much of the above and more by pasting your script into https://shellcheck.net. As the bash tag summary suggests, you should always try that before asking a shell question here because a lot of the time, it will solve your problem instantly.
I'm working on what should be a very simple BASH script. What I want to do is a pull an image from a webcamera using curl and write it to a file whose name is datestamped.
#! /bin/bash
DATE=$(date +%Y-%m-%d_%H-%M)
DIRECTORY1=home/manager/security_images/Studio_1/
TARGET1=${DIRECTORY1}${DATE}.jpg
curl http://web#192.168.180.211/snapshot.cgi > $TARGET1
When I try to run this I am told that there is no such file or directory. I believe this is due to an error in my escaping but I have tried seemingly every combination of quotation marks around the variables at each stage and still can't get it to work. I just don't understand what is going wrong and could really use some pointers towards what I'm doing wrong.
Many thanks
No, it’s just a typo.
DIRECTORY1=home/manager/security_images/Studio_1/
^^
Should be
DIRECTORY1=/home/manager/security_images/Studio_1/
of course.
As for escaping, even though only safe characters are used now, so quotes are technically superfluous, quoting out all $variables in every line by default is a good habit in shell scripting, there are very few cases when you do not want to use them.
Double quoting the redirection target should be enough:
curl http://web#192.168.180.211/snapshot.cgi > "$TARGET1"
Just make sure the path to it exists. You can run your script with
set -xv
to see how variables are interpolated.
Brand new to KornShell (ksh). I have an absolutely painful and hopefully simple problem.
I need to run a script with a string argument that includes single quotations mark and a variable. In the shell, it looks like this:
run_script -x '*082512*'
And that works fine.
But once I try to run it in a script with a variable for the date, I can not produce those single quotes. I have made the "today's date" variable without problem:
today=$(date "+%m%d%y")
But the problem occurs when I try to run the script. I have tried every possible combination of quotes within quotes and escaping the single quotes etc. etc. to no avail.
Any insight regarding this issue would be appreciated.
commenting here because the formatting is better.
Did you try
today=$(date "+%m%d%y")
run_script -x '*'"$today"'*'
As Glenn Jackman points out, quote are only 'seen' at the first level of shell invocation, where you typed in your command.
If the above doesn't help you, consider editing your question to show exact use case, with exact error messages or other non--expected behavior.
Good luck.