How to set a variable before running a command?
In a given shell, normally I’d set a variable or variables and then run a command. Recently I learned about the concept of prepending a variable definition to a command:
Can a command be assigned to a read variable?
Many pipelines that end with read variable can be converted into command substitutions, which will capture the output of a specified command. The output can then be assigned to a variable: This does not, unfortunately, work to split the text among multiple variables, as read does when given multiple variable arguments.
Why is setting an environment variable before a command not working?
This works… kind of. It doesn’t work when you’re changing a LC_* variable (which seems to affect the command, but not its arguments, for example, ‘ [a-z]’ char ranges) or when piping output to another command thusly:
What happens to the read variable in Bash?
When the read command sets the variable to the input, that variable is set only in the subshell, not the parent shell. When the subshell exits, the value of the variable is lost. Many pipelines that end with read variable can be converted into command substitutions, which will capture the output of a specified command.
How to assign a line to a variable?
When I run this line on the command prompt, it prints the total count of the number of processes which matches: example, the output of the above line is 2 in the command prompt. I want to write a shell script in which the output of the above line (2) is assigned to a variable, which will be later be used for comparison in an if statement.
What is the output of a shell script?
Closed 1 year ago. I am new with unix and I am writing a shell script. When I run this line on the command prompt, it prints the total count of the number of processes which matches: example, the output of the above line is 2 in the command prompt.
What happens when you change the environment variable in Bash?
Note that the environment variables will be restored/unchanged again when command finishes executing. Just be careful about about shell substitution happening, i.e. if you want to reference $FOO explicitly on the same command line, you may need to escape it so that your shell interpreter doesn’t perform the substitution before it runs env.