Assignment in subshells echo foo|read bar echo $bar Confusing time(1) for builtin time--format=%s sleep10 ~ in quotes rm"~/my file.txt" Single, quoted 'for' argument forfin"*.ogg"dorm $f;done Arithmetic truncation echo $((n/180*100)) Functions used externally f(){rm file...
A variable in single quotes'is treated as a literal string, and not as a variable. Variables in quotation marks"are treated as variables. To get the value held in a variable, you have to provide the dollar sign$. A variable without the dollar sign$only provides the name of the variable...
# echo variable BASH_VAR echo $BASH_VAR # meta characters special meaning in bash is suppressed when using single quotes echo '$BASH_VAR "$BASH_VAR"' 1. 2. 3. 4. 5. 6. 7. 8. 9. 16.3. Double Quotes Double quotes in bash will suppress special meaning of every meta characters exce...
When the original value of any expression is substituted by another value then it is called substitution. Bash variable substitution or parameter substitution is a very useful feature of bash. Generally, it is done in the bash by using the '$' character and the optional curly brackets ({})....
Enclosing characters in single quotes (‘'’) preserves the literal value of each character within the quotes. A single quote may not occur between single quotes, even when preceded by a backslash. 单引号包围的字符保留了在引号里面每个字符的字面意义。在单引号之间不允许出现单引号,即使这个单引号之...
Variables inside single quotesdo not expand -- and since awk code uses $ forcolumninstead ofvariable, you don't want them to expand! The shell would eat them all and change the meaning of the awk code. There's a couple ways to put variables into awk, none of which is embedding them...
The single quotes tell bash to print the characters specified within the quotes, i.e., the variable name. On the other hand, double quotes interpolate the input and display the variable's value. Note:The$character causes shell expansion and instructs bash to replace all the characters after ...
regex`trap'exit 42'sigint# Unportable signal speccmd &> file# Unportable redirection operatorreadfoo < /dev/tcp/host/22# Unportable intercepted filesfoo-bar() { ..; }# Undefined/unsupported function name[$UID= 0 ]# Variable undefined in dash/shlocalvar=value# local is undefined in shtim...
In contrast, single quotes show only the variable name instead. How to Use Substitution Command on Bash Command substitution, also known as variable substitution, is the process of allowing a command to run and its output to be pasted back as command-line arguments. For example, let us use ...
a=apple # a simple variable arr=(apple) # an indexed array with a single element and then echo the expression in the second column, we would get the result / behavior shown in the third column. The fourth column explains the behavior. ...