Bash assign comparison to variable

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How to assign a string value to a variable over multiple lines while indented? up vote 26 down vote favorite. Using quotes with single brackets Something like this: act="add" if [[ $act = "add" ]] then echo good else echo not good fi. 5. -eq. if [ "${INPUT}" == "flag" ]; then LABEL=${INPUT} fi echo ${LABEL} A binary comparison operator compares two variables or quantities. Bash catches undefined variables within double brackets, so quotes are not necessary. You can use variables as in any programming languages. " # Assignment using 'let' let a=16+5 echo "The value of \"a\" is now $a. # Bash permits integer For older versions of bash , use the following instead: server="$( printf '%s' "$1" | tr 'A-Z' 'a-z' )". A binary comparison operator compares two variables or quantities. up vote 1 down vote. Here's a pretty basic sample. OK, that seems fair enough but if that is true then #!/bin/bash # Naked variables echo # When is a variable "naked", i. is equal to. The export part states that it "exports to the environment of subsequently executed commands. When referencing a variable, it is generally advisable to enclose its name in double quotes. Using quotes with single brackets I would like to assign true/false to RUN in one line rather than using the clumsy if statement below. is equal to There is some blurring between the arithmetic and string comparisons, #+ since Bash variables are not strongly typed. Note that integer and string comparison use a different set of operators. This prevents reinterpretation of all special UNIX and Linux shell scripting, admin and programming help — Post awk, bash, csh, ksh, perl, php, python, sed, sh, shell scripts, and other shell scripting bash assign default value. A variable in bash can contain a number, a character, a string of characters. e. {LONG_VARIABLE_NAME:-hello}, but now bash also tries to execute 'hello' and that gives seems kludgy by comparison to the way the OP I have a variable called choice. -eq is for number comparison, use = for string comparison The right way to compare those two strings ( S1 and S2 ) using if is: if [ "$S1" = "$S2" ]. Quoting Variables. 1. The issue: Bash - assign array into variable as bash + compare variable with spaces. org/LDP/Bash-Beginners-Guide/html/sect_07_01. You can add or remove the quotes above, it does not make any difference. You have no need to declare a variable, just assigning a value to its reference will create it. html Shell script variables are by default treated as strings, not numbers, which adds some complexity to doing math in shell script. but Comparison get false , it is because spaces inside the variable . A variable in bash can contain a number, a character, a string of Other Comparison Operators. There are no data types. Code: : {DELETE:=false} : {FORCE:=false} : {S. " echo # In a 'for' loop (really, a type of disguised For older versions of bash , use the following instead: server="$( printf '%s' "$1" | tr 'A-Z' 'a-z' )". See: http://tldp. The latter OK, according to the bash manpage declare -x and export are equivalent. You can do all of this at once without using a variable: if [[ "not running" Note that using quotes does not determine whether you are comparing strings or numbers, the operator does. See test. Something like this: act="add" if [[ $act = "add" ]] then echo good else echo not good fi. Do not be stingy in use spaces in this case. " echo # In a 'for' loop (really, a type of disguised Variables. if [ "${INPUT}" == "flag" ]; then LABEL=${INPUT} fi echo ${LABEL} #!/bin/bash # Naked variables echo # When is a variable "naked", i. The jumphost variable will be set to whatever is in the first column of the first line in the file /home/Lists/srv matching the name of the server. What you want to do is: STAT="$( firewall-cmd --state )". # Assignment a=879 echo "The value of \"a\" is $a. # Bash permits #!/bin/bash # Naked variables echo # When is a variable "naked", i. if [ "$a" -eq There is some blurring between the arithmetic and string comparisons, #+ since Bash variables are not strongly typed. . -eq is for number comparison, use = for string comparison Single versus Double Brackets in bash This is because [[ ]] is a bash syntax construct, whereas [ ] is a program which happens to be implemented as an internal -- as such, cleaner syntax is possible with the former. Note: To check whether a variable is set and not blank, use -n "${BLAH}" rather than -n $BLAH . For you can get more details about string comparisons and test cases via 'man test'. Note that this only picks out the first match in the file and that the match If the output of firewall-cmd --state is not running , then the command STAT=$( firewall-cmd --state ) will set the variable STAT to the string not , and then try to execute running . Variables. This is probably easier and can cover more test cases. Integer comparison in Bash using if-else. The question clearly reads: How to set a variable equal to the output from a command in Bash? Assign AWK result to variable-1. integer comparison. A binary comparison != "gz" ] # Using bracket in variable These are similar to the Bash comparison operators I disagree with the "relevance" part. 8. , lacking the '$' in front? # When it is being assigned, rather than referenced. To keep with script n=6/3 $ echo $n 6/3 $ declare -i n $ n=6/3 $ echo $n 2 If BASH double parenthesis are not used, then the test command must be used to compare integer variables. How to check if a variable is set in Bash? 1869. " This, to me, suggests that these two give variables a greater scope, being shell-wide. please advice how to do it bash regular expiration. Note that this only picks out the first match in the file and that the match Note that using quotes does not determine whether you are comparing strings or numbers, the operator does