bashrc and export variables

Question

I am adding a variable that I want to be exported every time I run a terminal window. The problem is that it points to a file or directory that is not made at this time. But I want the bash to load and export the variable anyways because when I use it the file/folder will be there.

the variables

export ports=$(awk -F "/" 'BEGIN {ORS=","} /\/tcp/ {print $1}' nmap/initial.nmap | sed 's/,$//')
export portsf=$(awk -F "/" 'BEGIN {ORS=","} /\/tcp/ {print $1}' nmap/full.nmap | sed 's/,$//')

error messages:

awk: cmd. line:1: fatal: cannot open file `nmap/initial.nmap' for reading (No such file or directory)
awk: cmd. line:1: fatal: cannot open file `nmap/full.nmap' for reading (No such file or directory)

Is there any way to make this work through the bashrc or am I going to have make an alias that will export the variable I want each terminal session?

thanks for your time.

The command substitution runs immediately; it's not deferred until you actually want the value of ports. You'll have to wait until nmap/*.nmap exist to define the variables. — chepner
– chepner, Commented Jun 19, 2020 at 16:19
oh okay thanks!, i will have to set my exports to aliases and use them that way after I create the nmap/*.nmap. edit: alias --> echo "export string so at the very least copy and paste" thanks! — zach s
– zach s, Commented Jun 19, 2020 at 16:22
How would I do name function in the bashrc? would it be something like this? function ports() { export ports.... } export -f ports — zach s
– zach s, Commented Jun 19, 2020 at 16:38

chepner · Accepted Answer · 2020-06-19 16:48:33Z

1

Just add the following function to your .bashrc.

set_ports () {
    awk 'F "/" 'BEGIN {ORS=","} /\/tcp/ {print $1}' "$1" | sed 's/,$//'
}

Once the required files are availble, you can run

ports=$(set_ports nmap/initial.nmap)
portsf=$(set_ports nmap/full.nmap)
export ports ports

You can omit the last line if you don't actually need to export the variables (which I suspect is the case).

answered Jun 19, 2020 at 16:48

chepner

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1 Comment

zach s Over a year ago

thats what i have

jeremy · Accepted Answer · 2020-06-19 17:20:04Z

0

You could also check for existence of the files in your .bashrc and execute the exports command only if they exist. Something like this should work:

[ -f nmap/initial.nmap ] && export ports=$(awk -F "/" 'BEGIN {ORS=","} /\/tcp/ {print $1}' nmap/initial.nmap | sed 's/,$//')
[ -f nmap/full.nmap ] && export portsf=$(awk -F "/" 'BEGIN {ORS=","} /\/tcp/ {print $1}' nmap/full.nmap | sed 's/,$//')

what is after '&&' will be evaluated only if what is before '&&' exits with exit code 0. Concretely here for the first line for example, if the file 'nmap/initial.nmap' exists, you will indeed export the 'ports' variable and not otherwise.

answered Jun 19, 2020 at 17:20

jeremy

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