I'm trying to understand the command below, and particularly the parts that are in bold.
I understand what the second line is. It's testing if a file exists and if it doesn't, it creates one, but what does $_1/ mean?
test "$1" = "0" && exit test -f $_1/samplefile || touch $_1/samplefile $_1 means "expand the variable _1". Since this variable was not set, it will expand to nothing. Someone probably made a mistake.
It may be that the person thought $_1 would be the same as ${_}1, i.e., the expansion of $_, (which is the last argument to the previous command), concatenated with the number 1. But it is not the same, as can be seen below:
$ cat tst.bash #!/bin/bash test "$1" = "0" && exit echo $_ test "$1" = "0" && exit echo $_1 test "$1" = "0" && exit echo ${_}1 $ ./tst.bash 0 01 If you provide anything but the number 0 as an argument to the script (in the sample above, I provided no argument at all), then the test fails and exit is not triggered. So, for each echo, the last command executed is
test "$1" = "0" , whose last argument is 0. Thus, $_ expands to 0, ${_}1 expands to 01 and $_1 expands to the empty string.
$1 would be more sensible as part of the path since $_ would always be 0 in the second line, like your sample script shows. It doesn't seem like a simple typo, though, since it appears twice and I don't think _ is close to 1 or $ on the common keyboard layouts.. Thank you guys. I think that the person who wrote probably made a mistake. The propose was to check if there is a file and if not create a file. So, after some tries, I used test -f $(pwd)”/samplefile” || touch samplefile and it works. I just got confused because all commands are new for me, and I thought that maybe $_1/ could mean something. Thank you so much! :-)
_1=alpha _2=beta myCommandwith the intent that args to myCommand are in local environment, ordered but not positional, and are also global even within functions.