I am trying to perform a cURL command within a bash script to POST to a URI. The command requires that one of the arguments be surrounded by double and single quotes i.e. '"jsimmons"' In my script however this argument is a variable so the command keeps failing which I believe is because the variable is doing some weird expansion and the command is losing the quotes necessary.
For my current attempt, which doesn't work, the argument looks like, '""$watcher""' as I am trying to expand the variable and place that string within the double and single quotes.
How can I expand my variable properly to fulfill the requirements of the command?
If you have double quotes around your whole command, you can insert single quotes without any trouble but need to escape double quotes.
For example:
$ watcher=jsimmons
$ echo "'\"$watcher\"'"
'"jsimmons"'
You can escape the surrounding 's and "s with \
\'\"$watcher\"\'
Related
As per Change gnome-terminal title to reflect the current directory? I have tried to use:
PROMPT_COMMAND='echo -ne "\033]0;$(basename ${PWD})\007"'
... in my ~/.bashrc to indicate the name of the current directory in the gnome-terminal title bar.
For the most part it works fine; but if I try to open gnome-terminal from a directory like:
/run/user/1000/gvfs/mtp:host=%5Busb%3A001%2C008%5D/Internal shared storage/DCIM/Camera
... then it fails with:
basename: extra operand ‘storage/DCIM/Camera’
Try 'basename --help' for more information.
... every time the prompt is about to be shown in terminal.
Apparently the problem are the spaces in the directory name (even if the curly braces in ${PWD} should in principle obviate the need for quotes). So, I tried escaping with quotes, and it turns out it is not trivial (apparently just a single quote escape \"${PWD}\" does not work) - best I could get to is:
PROMPT_COMMAND='echo -ne "\033]0;$(basename \\\\"${PWD}\\\\")\007"'
... which works without an error - but it prints an extra backslash in the gnome-terminal title; for instance, in this case, the title is: Camera\.
What would be the correct construction of PROMPT_COMMAND, so it handles directories with spaces correctly, and it prints only the directory (e.g. Camera) without an appended backslash?
Why are you trying to escape your double quotes?
PROMPT_COMMAND='echo -ne "\033]0;$(basename "${PWD}")\007"'
would be correct. We can go through the levels of nesting:
top-layer single quotes. Inside single quotes, you do not need to escape double quotes. You would need to "escape" single quotes via '\'' (actually, this is string concatenation, but that's not relevant here).
second-layer double quotes. Inside double quotes, if you were trying to write literal ", you would need \". However, you have a third layer:
$() / command substitution. This layer, when executed, won't see the double quotes around it (single quotes would be a different story - you'd need '\''). Bash will correctly parse something like echo "$(echo "my variable is $foo")".
Also, the curly braces in ${PWD} have nothing to do with quotes. There is no difference between ${PWD} and $PWD from any point of view. Curly braces only come into play if your variable butts up against other "word" characters:
echo PWD_$PWD_USER_$USER // expands variables "USER" and "PWD_USER_"
echo PWD_${PWD}_USER_$USER // expands variables "USER" and "PWD"
I want to run a command from a bash script which has single quotes and some other commands inside the single quotes and a variable.
e.g. repo forall -c '....$variable'
In this format, $ is escaped and the variable is not expanded.
I tried the following variations but they were rejected:
repo forall -c '...."$variable" '
repo forall -c " '....$variable' "
" repo forall -c '....$variable' "
repo forall -c "'" ....$variable "'"
If I substitute the value in place of the variable the command is executed just fine.
Please tell me where am I going wrong.
Inside single quotes everything is preserved literally, without exception.
That means you have to close the quotes, insert something, and then re-enter again.
'before'"$variable"'after'
'before'"'"'after'
'before'\''after'
Word concatenation is simply done by juxtaposition. As you can verify, each of the above lines is a single word to the shell. Quotes (single or double quotes, depending on the situation) don't isolate words. They are only used to disable interpretation of various special characters, like whitespace, $, ;... For a good tutorial on quoting see Mark Reed's answer. Also relevant: Which characters need to be escaped in bash?
Do not concatenate strings interpreted by a shell
You should absolutely avoid building shell commands by concatenating variables. This is a bad idea similar to concatenation of SQL fragments (SQL injection!).
Usually it is possible to have placeholders in the command, and to supply the command together with variables so that the callee can receive them from the invocation arguments list.
For example, the following is very unsafe. DON'T DO THIS
script="echo \"Argument 1 is: $myvar\""
/bin/sh -c "$script"
If the contents of $myvar is untrusted, here is an exploit:
myvar='foo"; echo "you were hacked'
Instead of the above invocation, use positional arguments. The following invocation is better -- it's not exploitable:
script='echo "arg 1 is: $1"'
/bin/sh -c "$script" -- "$myvar"
Note the use of single ticks in the assignment to script, which means that it's taken literally, without variable expansion or any other form of interpretation.
The repo command can't care what kind of quotes it gets. If you need parameter expansion, use double quotes. If that means you wind up having to backslash a lot of stuff, use single quotes for most of it, and then break out of them and go into doubles for the part where you need the expansion to happen.
repo forall -c 'literal stuff goes here; '"stuff with $parameters here"' more literal stuff'
Explanation follows, if you're interested.
When you run a command from the shell, what that command receives as arguments is an array of null-terminated strings. Those strings may contain absolutely any non-null character.
But when the shell is building that array of strings from a command line, it interprets some characters specially; this is designed to make commands easier (indeed, possible) to type. For instance, spaces normally indicate the boundary between strings in the array; for that reason, the individual arguments are sometimes called "words". But an argument may nonetheless have spaces in it; you just need some way to tell the shell that's what you want.
You can use a backslash in front of any character (including space, or another backslash) to tell the shell to treat that character literally. But while you can do something like this:
reply=\”That\'ll\ be\ \$4.96,\ please,\"\ said\ the\ cashier
...it can get tiresome. So the shell offers an alternative: quotation marks. These come in two main varieties.
Double-quotation marks are called "grouping quotes". They prevent wildcards and aliases from being expanded, but mostly they're for including spaces in a word. Other things like parameter and command expansion (the sorts of thing signaled by a $) still happen. And of course if you want a literal double-quote inside double-quotes, you have to backslash it:
reply="\"That'll be \$4.96, please,\" said the cashier"
Single-quotation marks are more draconian. Everything between them is taken completely literally, including backslashes. There is absolutely no way to get a literal single quote inside single quotes.
Fortunately, quotation marks in the shell are not word delimiters; by themselves, they don't terminate a word. You can go in and out of quotes, including between different types of quotes, within the same word to get the desired result:
reply='"That'\''ll be $4.96, please," said the cashier'
So that's easier - a lot fewer backslashes, although the close-single-quote, backslashed-literal-single-quote, open-single-quote sequence takes some getting used to.
Modern shells have added another quoting style not specified by the POSIX standard, in which the leading single quotation mark is prefixed with a dollar sign. Strings so quoted follow similar conventions to string literals in the ANSI standard version of the C programming language, and are therefore sometimes called "ANSI strings" and the $'...' pair "ANSI quotes". Within such strings, the above advice about backslashes being taken literally no longer applies. Instead, they become special again - not only can you include a literal single quotation mark or backslash by prepending a backslash to it, but the shell also expands the ANSI C character escapes (like \n for a newline, \t for tab, and \xHH for the character with hexadecimal code HH). Otherwise, however, they behave as single-quoted strings: no parameter or command substitution takes place:
reply=$'"That\'ll be $4.96, please," said the cashier'
The important thing to note is that the single string that gets stored in the reply variable is exactly the same in all of these examples. Similarly, after the shell is done parsing a command line, there is no way for the command being run to tell exactly how each argument string was actually typed – or even if it was typed, rather than being created programmatically somehow.
Below is what worked for me -
QUOTE="'"
hive -e "alter table TBL_NAME set location $QUOTE$TBL_HDFS_DIR_PATH$QUOTE"
EDIT: (As per the comments in question:)
I've been looking into this since then. I was lucky enough that I had repo laying around. Still it's not clear to me whether you need to enclose your commands between single quotes by force. I looked into the repo syntax and I don't think you need to. You could used double quotes around your command, and then use whatever single and double quotes you need inside provided you escape double ones.
just use printf
instead of
repo forall -c '....$variable'
use printf to replace the variable token with the expanded variable.
For example:
template='.... %s'
repo forall -c $(printf "${template}" "${variable}")
Variables can contain single quotes.
myvar=\'....$variable\'
repo forall -c $myvar
I was wondering why I could never get my awk statement to print from an ssh session so I found this forum. Nothing here helped me directly but if anyone is having an issue similar to below, then give me an up vote. It seems any sort of single or double quotes were just not helping, but then I didn't try everything.
check_var="df -h / | awk 'FNR==2{print $3}'"
getckvar=$(ssh user#host "$check_var")
echo $getckvar
What do you get? A load of nothing.
Fix: escape \$3 in your print function.
Does this work for you?
eval repo forall -c '....$variable'
I want to run a command from a bash script which has single quotes and some other commands inside the single quotes and a variable.
e.g. repo forall -c '....$variable'
In this format, $ is escaped and the variable is not expanded.
I tried the following variations but they were rejected:
repo forall -c '...."$variable" '
repo forall -c " '....$variable' "
" repo forall -c '....$variable' "
repo forall -c "'" ....$variable "'"
If I substitute the value in place of the variable the command is executed just fine.
Please tell me where am I going wrong.
Inside single quotes everything is preserved literally, without exception.
That means you have to close the quotes, insert something, and then re-enter again.
'before'"$variable"'after'
'before'"'"'after'
'before'\''after'
Word concatenation is simply done by juxtaposition. As you can verify, each of the above lines is a single word to the shell. Quotes (single or double quotes, depending on the situation) don't isolate words. They are only used to disable interpretation of various special characters, like whitespace, $, ;... For a good tutorial on quoting see Mark Reed's answer. Also relevant: Which characters need to be escaped in bash?
Do not concatenate strings interpreted by a shell
You should absolutely avoid building shell commands by concatenating variables. This is a bad idea similar to concatenation of SQL fragments (SQL injection!).
Usually it is possible to have placeholders in the command, and to supply the command together with variables so that the callee can receive them from the invocation arguments list.
For example, the following is very unsafe. DON'T DO THIS
script="echo \"Argument 1 is: $myvar\""
/bin/sh -c "$script"
If the contents of $myvar is untrusted, here is an exploit:
myvar='foo"; echo "you were hacked'
Instead of the above invocation, use positional arguments. The following invocation is better -- it's not exploitable:
script='echo "arg 1 is: $1"'
/bin/sh -c "$script" -- "$myvar"
Note the use of single ticks in the assignment to script, which means that it's taken literally, without variable expansion or any other form of interpretation.
The repo command can't care what kind of quotes it gets. If you need parameter expansion, use double quotes. If that means you wind up having to backslash a lot of stuff, use single quotes for most of it, and then break out of them and go into doubles for the part where you need the expansion to happen.
repo forall -c 'literal stuff goes here; '"stuff with $parameters here"' more literal stuff'
Explanation follows, if you're interested.
When you run a command from the shell, what that command receives as arguments is an array of null-terminated strings. Those strings may contain absolutely any non-null character.
But when the shell is building that array of strings from a command line, it interprets some characters specially; this is designed to make commands easier (indeed, possible) to type. For instance, spaces normally indicate the boundary between strings in the array; for that reason, the individual arguments are sometimes called "words". But an argument may nonetheless have spaces in it; you just need some way to tell the shell that's what you want.
You can use a backslash in front of any character (including space, or another backslash) to tell the shell to treat that character literally. But while you can do something like this:
reply=\”That\'ll\ be\ \$4.96,\ please,\"\ said\ the\ cashier
...it can get tiresome. So the shell offers an alternative: quotation marks. These come in two main varieties.
Double-quotation marks are called "grouping quotes". They prevent wildcards and aliases from being expanded, but mostly they're for including spaces in a word. Other things like parameter and command expansion (the sorts of thing signaled by a $) still happen. And of course if you want a literal double-quote inside double-quotes, you have to backslash it:
reply="\"That'll be \$4.96, please,\" said the cashier"
Single-quotation marks are more draconian. Everything between them is taken completely literally, including backslashes. There is absolutely no way to get a literal single quote inside single quotes.
Fortunately, quotation marks in the shell are not word delimiters; by themselves, they don't terminate a word. You can go in and out of quotes, including between different types of quotes, within the same word to get the desired result:
reply='"That'\''ll be $4.96, please," said the cashier'
So that's easier - a lot fewer backslashes, although the close-single-quote, backslashed-literal-single-quote, open-single-quote sequence takes some getting used to.
Modern shells have added another quoting style not specified by the POSIX standard, in which the leading single quotation mark is prefixed with a dollar sign. Strings so quoted follow similar conventions to string literals in the ANSI standard version of the C programming language, and are therefore sometimes called "ANSI strings" and the $'...' pair "ANSI quotes". Within such strings, the above advice about backslashes being taken literally no longer applies. Instead, they become special again - not only can you include a literal single quotation mark or backslash by prepending a backslash to it, but the shell also expands the ANSI C character escapes (like \n for a newline, \t for tab, and \xHH for the character with hexadecimal code HH). Otherwise, however, they behave as single-quoted strings: no parameter or command substitution takes place:
reply=$'"That\'ll be $4.96, please," said the cashier'
The important thing to note is that the single string that gets stored in the reply variable is exactly the same in all of these examples. Similarly, after the shell is done parsing a command line, there is no way for the command being run to tell exactly how each argument string was actually typed – or even if it was typed, rather than being created programmatically somehow.
Below is what worked for me -
QUOTE="'"
hive -e "alter table TBL_NAME set location $QUOTE$TBL_HDFS_DIR_PATH$QUOTE"
EDIT: (As per the comments in question:)
I've been looking into this since then. I was lucky enough that I had repo laying around. Still it's not clear to me whether you need to enclose your commands between single quotes by force. I looked into the repo syntax and I don't think you need to. You could used double quotes around your command, and then use whatever single and double quotes you need inside provided you escape double ones.
just use printf
instead of
repo forall -c '....$variable'
use printf to replace the variable token with the expanded variable.
For example:
template='.... %s'
repo forall -c $(printf "${template}" "${variable}")
Variables can contain single quotes.
myvar=\'....$variable\'
repo forall -c $myvar
I was wondering why I could never get my awk statement to print from an ssh session so I found this forum. Nothing here helped me directly but if anyone is having an issue similar to below, then give me an up vote. It seems any sort of single or double quotes were just not helping, but then I didn't try everything.
check_var="df -h / | awk 'FNR==2{print $3}'"
getckvar=$(ssh user#host "$check_var")
echo $getckvar
What do you get? A load of nothing.
Fix: escape \$3 in your print function.
Does this work for you?
eval repo forall -c '....$variable'
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 run with the file with command line arguments:
samplebash.bsh fakeusername fakepassword&123
.bsh file:
echo "Beginning script..."
argUsername='$1'
argPassword='$2'
protractor indv.js --params.login.username=$argUsername --params.login.password=$argPassword
Output:
Beginning script...
123: command not found
The Issue: For some reason, it interprets what follows the & symbol from the password as a command, how do I avoid this?
The problem isn't happening in your script, it's happening in your original command line. & is a command terminator, which specifies that the command before it should be executed in the background. So your command was equivalent to:
samplebash.bsh fakeusername fakepassword &
123
You need to quote the argument to prevent special characters from being interpreted by the shell.
samplebash.bsh fakeusername 'fakepassword&123'
Also, you shouldn't put single quotes around a variable like you do in your assignments, that prevents the variable from being expanded. So it should be:
argUsername=$1
argPassword=$2
And you should put double quotes around the variables when you use them in the command, to prevent wildcards and whitespace from being interpreted.
protractor indv.js --params.login.username="$argUsername" --params.login.password="$argPassword"
As a general rule, you should always put double quotes around variables unless you know they're not needed.