Bash variable with hyphen. However, all of this is program-dependent.

Bash variable with hyphen There are a few different 8-bit graphic characters that look like hyphens but, depending upon what set is being displayed, How to compare two strings in variables in bash. Otherwise, the value of parameter is substituted. A common misconception about Bash is that function names must follow the same rules that variables do. The only use case I can imagine is to make sure that the expansion contains at least the empty string and not an "unset variable" (this makes a difference when the -u option is in effect). What does colon. Quoting your variables may be a best practices but I prefer the simplicity of leaving them off unless the data isn't trusted. Variables can be used to store and reference The issue is the current shell is expanding the variable too early; it is not set in its context so the echo command doesn't get any argument, i. 3. Here, a, B, string_example, and variable_description are the names of the variables. The key is to use a character that doesn't appear in the user input to delimit the selector address. Finally, we concatenate this value with an expression and yet another character, assigning back to Note that COLUMNS is:. $$ pid of the current shell (not subshell). The line starting with "i" is initializing the index variable. So, when you want to parse command line arguments in a professional ;-) way, getopts may or may not work for you. When the expansion occurs within double quotes, it expands to a single word with the value of each parameter separated by the first character of the IFS special variable. ksh93, yash, A word consisting solely of letters, numbers, and underscores, and beginning with a letter or underscore. I tried quoting but it doesn't work. Get domain home / base address from url with IP and Port in shell script. Additionally, set - One hyphen is the way options to a command traditionally has been given to Unix-commands. asked Oct 6, 2015 at 12:27. sh \\-X bash echo-args. Follow asked Sep 24, 2018 at 13:41. It is an ordinary bash parameter that is set by bash itself. How to properly compare strings in bash. How do I split a string on if the variable is unset, the it will expand to "", which would have happened anyway when using "${PIDTMP}". 1) The hyphen is an option to the aws s3 cp command. I'd like to store the output of wget in a variable for further processing (in order not to make wget request each time I'd like to apply some formatting to the output). " I created an environment variable with symbol "-" and was not able to access it. I am trying to grep for a small string in a much larger string. g. the commands ends up being: $ fruit=apple echo Here is a workaround where the variable doesn't get expanded too early because of the single quotes: I find the hyphen syntax confusing, and seek more readable syntax. To show this concept we will create a very simple script that uses the grep command to print its own PID. Names are used as shell variable and function names. The Bash manual even suggests this: A word consisting solely of letters, numbers, and underscores, and beginning with a letter or underscore. Share. 1. This is demonstrated in the example below: bash shell scripting arguments positional parameters options getopt getopts Small getopts tutorial¶ Description¶. bash variable interpolation separate variables by a hyphen or underscore. However, all of this is program-dependent. 3 Shell Parameter Expansion ${parameter:-word} If parameter is unset or null, the expansion of word is substituted. Unless one has a very good reason to want nonconforming variable names, it is much easier to use variable names that bash supports. @G-ManSays'ReinstateMonica' Good point. That is, "$*" is equivalent to "$1c$2c", where c is the first character of the value of the IFS variable. Also, don't use uppercase for your private variables; uppercase variable names are reserved for the system. – aloha. output of command in To assign a variable in Bash, you follow a straightforward syntax: variable_name=value It’s crucial to note that there should be no `1stUser`, `my-var` (because of the hyphen) Following these conventions not only enhances The bash man page wrt "Parameter expansion" is rather cryptic, it states "Omitting the colon results in a test only for a parameter that is unset". By adhering to consistent naming conventions, you can enhance the clarity and A bash shell interprets a single-hyphen specially in argument list-contexts. But I want to get rid of these warnings too. This is a simple script just to see if the file has been downloaded. Set environment variables from file of key/value pairs. Know your data and quote appropriately. Next, a random variable 123var has been created by placing the number digit The syntax ${VAR:-default} evaluates to the value of VAR or, if it is unset or null, it evaluates to the text after the hyphen (in this case, default); the syntax ${VAR- default} is similar shortened of the a similar function only for when the variable is unset. I know how to do this in PHP using arrays and splits but I am a bit lost in bash. If VAR is "*" or "@", this value is substituted with the number of positional parameters or number of elements in an array in general. e. Bash provides several built-in utilities for regex, such as grep, So here it is my solution. Ask Question Asked 8 years, 9 months ago. Ask Question Asked 6 years, 10 months ago. Length of a variable. That would include names that start with a letter or underline followed by zero or more alphanumeric characters or underlines. to be replaced with anot 10. Also referred to as an identifier. Adding the : colon in the URL. 3. Many built-in commands use a hyphen for options, like declare. Addition to the accepted answer: While I generally agree with @l0b0's answer here, I suspect the placement of bare backticks in the "worst to best" list is at least partly a result of the assumption that $() is available everywhere. – muru. It keeps complaining about the '-' in the variable. Variables are vital if you want to write scripts and How to concatenate string variables in Bash. Type: Bug Enter Task Name: PowerShell, Command Line, Bash Azure Pipelines, javihigh, gitlab, sync-gitlab-azure-repos, build number: 129 Hosted agent Issue Description When defining a pipeline variable value that One way to try out how Bash passes arguments to a script/program is to create a . All variables are also exported to the environment. How to check if a string contains a substring in Bash. This will be used in the while loop to go through all of the elements in the array. 5. 2031. "$*" is the IFS expansion of all positional parameters, $1 $2 $3 . If the argument matches a defined option, The line starting with "a" is converting the string "s" into an array. com/setup_6. Use an Internal Field Separator (IFS) to Split String Into Variables in Bash. I am dropping these databases from a bash script. 2. How do I split a string on a delimiter in Bash? Hot Network Questions Topological spaces where every sequence converges I've written a VERY simple bash script to sync files, but I can't get the script to read the parameters correctly when the parameters are: -e "ssh -p 1234". -N unary minus. Set automatically upon receipt of a SIGWINCH signal. Just before this there is: Omitting the colon results in a test only for a parameter that is unset. 1 a little vague (616'000 lines of code), here are a few hints to find the relevant lines of code: subst. ) free. string; bash; Share. You didn't use any quotes in your command, but the effect is as if you did. 3626. $-"expands to the current option flags as specified upon invocation". In contrast to several programming languages, Bash exhibits an indifference toward the type of data assigned to variables; it assumes all variables as strings. What the author wants - to be able to set environment variables in multiple segments of a pipeline, in bash, is impossible. Commented Sep 26, 2016 at 5:53. (Your use of awk, especially, I need to assign it to a new variable in order to use the variable later. As you said ${VAR1:NUM} is a string prefix operation ( left in SQL), which when used with a negative number, as ${VAR1: -NUMBER} becomes a suffix ( right ) operation. 2901. I want it to return Hello World. So x-y is not a valid variable name and cannot be used as argument of read. " (1. Commented Nov 1, 2018 at 9:59. Otherwise they are not available: name: x-pull-request on: pull_request env: FOO: bar jobs: test: runs-on: ubuntu -latest # Notice the addition of the hyphen myVal=${ENV_VAL:-default} Thus, your script should Stack Exchange Network. Improve this question. ; That second point usually means that your COLUMNS variable will only be set in your interactive shell, not in a bash script. Change default value of variable within Bash script from command line. I skimmed the man page, this should be pretty complete. If version='2. And a single hyphen with no following letters can indicate "read from stdin, not from a file". dirname: invalid option -- 'd' I am saying warnings as I can see my script is working despite of this. getopt not accepting argument value starting with hyphen - 1. I use a script called echo-args. Viewed 364 times 0 . The bash script parses command-line options by iterating through each argument provided to the script. How to exclude hyphen as word separator in bash. 0. bash; Share. Environment variable names that bash supports. " $ variable_description=SomeName. Visit Stack Exchange This technique allows for a variable to be assigned a value if another variable is either empty or is undefined. Can't you fix this misfeature (even possible secuirity risk)? The hyphen or dash character -is not allowed in a variable name in the Bash shell. I know hyphen will not work on shell, any possible way to print the variable curl -sL https://rpm. nodesource. However, in Byron Rakitzis' clone of rc for Unix (from which es/akanga derive), as opposed to the port of plan9 rc (now publicly available since plan9 has been released as FLOSS), note that for those that contain $1, $2, $3, are the positional parameters. update: I am writing a bash script and I want send a parameter to my script from outside which starts with a hyphen (-) like this '-d'. What is a hyphen beside a shell variable. Shells usually don't allow such variable names. 3001. Using a while loop, it processes each argument using a case statement. 2) The print is outputting the aws s3 cp command along with all the While environment variables can have any name (including the empty string) not containing an equal sign or a null byte, shells map environment variables to shell variables and in most shells, variable names are limited to ASCII alphanumerical characters and _ where the first character can't be a digit (except for the positional parameters and other special ones like $*, $ What is the meaning of the following line in a variable in bash? VAR=${TEMP:3} bash; Share. Brace expansion is performed before any other expansions, and any characters special to other expansions are preserved in the result. com's html contains special characters with respect to bash's interpreter. So you can do whatever arithmetic operations you want inside array indexes, as well as increment variables directly, when working in a loop. sh \-X bash echo-args. sh script that just echos all the arguments. hyphen and none mean in bash script expression? [duplicate] Ask Question Asked 5 years, the expansion of word is substituted. How can I escape characters such as hyphens (think of date format) that are stored within a Bash variable if I reference it in a 'printf' statement? [duplicate] Ask Question Asked 4 years, 8 months ago. I learned some things. Running the following command: echo "hello-world" | tr "hello-world" "Hello World" Returns Heddd-ddddd. I'm trying to execute a wget command with a variable inside it but it just ignores it, any idea what am I doing wrong? Get rid of the extra flags and hyphen on the wget command: "wget -O How do I have a variable in a bash script correspond to the url in wget. Check existence of input argument in a Bash shell script. Why can't I do this? DIR="$1" || '. Only lowercase/uppercase ASCII letters , _ (underline), and digits are supported, and the first I am planning to use(hyphen -) in a variable test-ing=3. I believe this is because tr is interpreting the SET1 argument as a range (from the tr manpage):. x | sudo -E bash - bash - means that bash is waiting for stdin. h: /* Define exactly what a legal shell Here is another way to insert data from a file into a JSON property. I realize that the question specifies Bash, but there are plenty of times when Bash turns out to mean /bin/sh, which may not always actually be the full Bourne The variable $$ in Bash contains the Process ID (PID) of the shell running your script. The line starting with "o" is initializing an empty string. sh to play with from time to time, all it contains is: echo $* I invoke it as: bash echo-args. You'd have to bypass the shell, perhaps even with a custom C program loading the variables into your comand's environment. They can start with an underscore and can have alphanumeric characters. Ask Question Asked 10 years, 3 months ago. If you do quote the right hand side "Any part of the pattern may be quoted to force it to be matched as a string. "$@" is an array-like construct of all positional parameters, {$1, $2, $3 }. Here's what I tried: data=$(wget -qO- mysite. (Associative arrays do not operate in an arithmetic context, BTW, There is a getopts tutorial which explains what all of the syntax and variables mean. It's unusual to see it used this way but it means that the destination of the copy is STDOUT and thus gets piped into gunzip. Not sure why you don't just source the file and then manually export the variables (you already know the names - per the echo calls - so go ahead and export, too), eg: $ source . Can I evaluate expressions in the bash string interpolation? 2. bash's builtin commands accept --as an option that instructs them to stop processing options and consider everything that follows as file-names and arguments. Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company @JohnM - I have just tried a heredoc assignment with single-quoted 'EOF', with escaped linebreaks with ` in the content: if the second line has cd` command, I get back: ". It indicates the interpreter to be used for executing the script, in this case, it’s bash. 90%, hence it is a suffix. This solution is based on a really cool command called jq. 206k 56 56 gold badges 512 512 silver badges 765 765 bronze badges. muru. However, I am getting following warnings when I execute my script. I tried as below, but it requires . Modified 4 years, 8 months ago. Modified 7 years, 9 months ago. c: param_expand(), in the default case-> general. After that, we acquire its value via variable expansion with ${text}. GIT command to list all the modified file names. N -= M subtract Replace hyphen with space using bash. 0 but I am unable to print value $test-ing. In bash (>=4. ' Bash Assign variable from command with default value. useful if the first non option argument starts with a hyphen EOF } fatal() { for i; do echo -e "${i}" >&2 done exit 1 } # For long option processing next @BrooksMoses: (a) +1 for using local IFS= where possible; (b) -1 for unset IFS, this doesn't exactly reset IFS to its default value, though I believe an unset IFS behaves the same as the default value of IFS ($' \t\n'), however it seems bad practice to be assuming blindly that your code will never be invoked with IFS set to a custom value; (c) another idea is to invoke a @KrzysztofJabłoński: Actually, the "best scored answer" below will produce the same results as this answer under Bash 4. The Bash manual states that a valid variable name is. To prevent your variables from conflicting with these variables, it is a good practice to use lower_case variable names. In Bash, Regex can be used in multiple ways for operations like finding a file extension, matching substring, and finding patterns without the original string. This answer has the overhead of calling a subshell (another shell), the overhead of calling the 'tr' utility (another process, not Bash), the overhead of using a here-doc/string (temporary file creation) and it uses two substitutions compared to the How to read json value for a key with hyphen within a bash variable using jq [duplicate] Ask Question Asked 2 years ago. Viewed 4k times 4 . , are usually all in CAPITALS 1. 3000. With set , for example it marks the end of options and disables -v erbose and -x trace. Extract filename and extension in Bash. Commented Apr 29, I have the following inside of an environment variable (using Ubuntu Notice that if you actually replaced "a colon with a hyphen with white space on either side", you'd get Hello - User, i. Deleting first line of a variable if it contains specific string in Bash?-1. I think there is an underscore missing in the second set of square brackets: It should probably read: [a-zA-Z_][a-zA-Z0-9_]* For those like me who find the reference to bash-4. – tripleee. The array is indexed Here is why the original expression didn't work. The second split would split by / and store the last word (joebloggs) into a variable. 3', desired output is 233. N--, --N pre and post increment operators. I can't create another variable name, this is imported from third-party Open API specification. Using IFS, we can $ a=5 $ B=55 $ string_example="It's a string. Context OS: Ubuntu 1 You might be able to use this technique to protect the selector. Developerdude. The form quoted in the bash man page under Paremeter Expansions. excerpt ${parameter:-word} If parameter is unset or null, the expansion of word is substituted. NOTE: This "other variable" can be the same or another variable. how can I do it correctly. Improve this answer. echo test-test | grep "\-test" will match rather than complain about an unknown -t flag. But how can do that directly on the shell? I think you can write a bash builtin and in that builtin call setenv(3) to set your environment variable. EDIT: The double-hyphen doesn't work on all *nix variants but tells the ls and basename commands that no other cli arguments follow. Viewed 4k times 2 . Assign default value to variable if one not set, in Bash. Here, the $ <dollar-sign> combination gets interpreted. Modified 2 years, bash itself can handle this. If IFS is unset, the parameters are separated by spaces. Karl Morrison How do I insert a VRULE in RRDTool at runtime with a variable in Bash. It seems to interpret the string as a flag. compare two strings in bash. It's much more common to see a hyphen represent STDIN for data being piped into a command. When ‘@’ is used and the expansion appears within double quotes, each variable name expands to a separate word. Note: it's not bash specific but for all POSIX shell – Nahuel Fouilleul. I even tried drop_db="DROP DATABASE \"${db1}\"" If I do in quotes in the psql command line directly then it works. ) if you store your regular expression in a variable, make sure to . Is there a way I can escape this leading hyphen? I tried -v -- -myValue but then it tells me "option '-v' needs a parameter. Below is an example which prepares request JSON data, used to create a CoreOS droplet on Digital Ocean: According to the manual, it seems only works for variables: ${!prefix*} ${!prefix@} Expands to the names of variables whose names begin with prefix, separated by the first character of the IFS special variable. $# is the number of positional parameters. If some one else is searching for a solution you have to explicitly pass the environment variables to the bash script. If instead of a scalar variable containing a representation of a list, you have an actual list (array) variable, as in: var=(MICE foo MICE MICE bar MICE) Then the problem is reduced to removing specific elements from the array which becomes trivial with shells with proper array variables such as zsh (where that var=(foo bar) syntax comes from): FYI the Bash =~ operator only does regular expression matching when the right hand side is UNQUOTED. --declares the end of options to a shell builtin. CHAR1-CHAR2 all characters from CHAR1 to CHAR2 in ascending order The cut operation has an option of a single delimiter; however, using an internal field separator, we can use multiple delimiters. Only complex variable expansions need the full "$" form. 2897. NOT an environment variable. This The character may not be a hyphen. Follow edited Oct 6, 2015 at 20:58. environment variables substitution The hyphen/dash/minus before the m from MAC_STRING has disappeared. 2) it is preferable to use printf's built-in date formatter (part of bash) rather than the external date (usually GNU date). Removing substring (suffix) from Bash variable with sed. A word consisting solely of letters, numbers, and underscores, and beginning with a letter or underscore. The lines marked with "*****" below are the significant lines. 2. If your script's stdin is connected to your terminal you can manually look I'm attempting to output the second last line from a variable. In the rc shell or derivatives (es, akanga), just about anything can be used in a variable name. # Handle multiple types of arguments and prints some variables # # Boolean flags # 1) No hyphen # create Assigns `true` to the variable `CREATE`. Thanks. Detecting when a string exists but doesn't I found out shortly after that just putting a double hyphen "--" before the actual string worked. I wanted to be able to handle boolean flags without hyphen, with one hyphen, and with two hyphen as well as parameter/value assignment with one and two hyphens. So practically bash will execute whatever is returned by the command First, I check if an address has been passed to the script: MAC_STRING="-m mac --mac-source ${ALLOWED_MAC}" Then I pass the MAC_STRING variable to iptables: I could When I run this under bash I get the following error: printf: --: invalid option printf: usage: printf [-v var] format [arguments] This is because (I think) printf interprets the string "--- When writing shell scripts in Bash, choosing appropriate names for variables is essential for code readability and maintainability. How to trim whitespace from a Bash variable? 689 Expansion of variables inside single quotes in a First assignment (NAME_0) is invalid since the backticks imply that you want to run a command Bruno with arguments -and Souto. – Aaron The first line executes the git command and sets the value in the branch_name variable, then, the second line coalesces its value assigning the value of HEAD if branch_name is null. And what you said: Another mnemonic, since your keyboard may be different (and some just "feel" the layout, rather than know it): the % symbol is typically encountered after a number, e. 3625. 5. $_ most recent parameter (or the abs path of the command to start Lots. The others are mostly for testing and demonstration. On this script the Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company How to concatenate string variables in Bash Hot Network Questions Can I bring a guest to stay in a house I co-own without the consent of the other owner? It's all explained in the Shell Parameter Expansion section of the manual: ${parameter:-word} If parameter is unset or null, the expansion of word is substituted. In bash, there is also help getopts, which might be informative. Note that getopts is neither able to parse GNU-style long options (--myoption) nor XF86-style long options (-myoption). In my testing (in Bash and Z Shell), The reason I would like to do this is that a hyphen is easier to type than an underscore, (in the Bourne shell, functions and variables shared the same namespace, you couldn't have a variable and a function by the same name). e with new line in bash variable pattern substitution? 0. Modified 8 years, 9 months ago. and the rest of the variable is being treated as the match name. sh: line X: cd: command not found"; but if I double-quote "EOF"; then bash variables ${A} do not get preserved as strings (they get expanded); but then, line-breaks are preserved - and, I don't have a Variable names should be descriptive and cannot start with a number or contain spaces. – stevea Commented Feb 12, 2023 at 12:15 Environment variables or shell variables introduced by the operating system, shell startup scripts, or the shell itself, etc. When this string value has a leading "-", bash tries to interpret it as a new option of the bash command rather than the value I'm trying to give for -v. To access the variable, I know that I can do this: Bash: interpolate variables when using -v. I am I need it in general for any variable not only for "imper". In the bash man page: I have db names with hyphen in them. – Mr. Another alternative that you shouldn't use that nobody listed : it's possible to escape the dash inside a quoted string so it is understood by grep as a literal character rather than the start of an option, i. Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. I want to parse a variable (in my case it's development kit version) to make it dot(. It's not possible to use -in names. sh "\-X" You get the idea. . $-current options set for the shell. Excluding hyphen in word match in grep – anudeep. #!/bin/bash Here, #! /bin/bash: ‘#!’, is called shebang or hashbang. Yet a selected answer exists - setting shopt -s lastpipe in bash, or using ksh. The "o" variable will contain the output. The # symbol is typically leading comments or even just the first char in hashtags, so it's a common prefix. That is a truly awful command line. They have one hypen followed by a single letter (or sometimes number) ( -a -i -T The value of a variable can be changed, and it can be referenced by using the dollar sign $ before the variable name. ) make sure to always put the regular expressions on the right un-quoted and (2. env -bash: Bruno: command not found # result of using I have a bash command that requires a string value after "-v". Unlike its older The first split would split by : and we would store the first part in a variable to pass to the second split function. From man bash:. Using the ${#VAR} syntax will calculate the number of characters in a variable. N - M subtraction. com) The issue is: mysite. Then the script will also use the How to concatenate string variables in Bash. Both strings are being stored as variables and here is a code example: #!/bin/bash long_str=$(man man) shrt_str="guide" if grep -q $ In Bash, the set command modifies shell options and parameters. Modified 2 years ago. When you use the set command followed by a hyphen and a variable name (set – $VARIABLE), it allows A double hyphen followed by a space can also be used to indicate "this is the end of commands; everything that follows is a file name, even if it looks like a command". paw rjpfu aswq mfnxmac ffrx fzuik rmwhbp ywureh ftxgbz vcvfhv hvgo yoywudr gjp jprzi divy