execute the string str as a command

sh

eval str

"everything except file1"

sh

[^file1]*

how do you redirect to standard error?

sh

>&2

How do you make your script clean up itself after it receives a termination signal?

sh

create a clean_up() function that cleans things up, and write at the beginning of the program:

What does (command) mean?

sh

command is run in a subshell. Variable declarations and directory changes won't persist in the current shell.

run a command in a subshell

sh

(command)

find: execute command1 and command2

sh

find ... -exec command1 \; -exec command2 \;

given variable string, with spaces, retrieve its first word

sh

echo $string | awk '{print $1;}'

(awk) what is $0?

sh

the whole string

for i in ...; do

sh

{1..100}

for i in ...; do

sh

{100..1}

difference between chmod and chown

sh

chmod: changes the permission for user, group, other

what happens to errors in scripts by default?

sh

they're ignored

explain <<

sh

here document. Used like this:

explain <<<

sh

here string.

difference between << and <<<

sh

<< begins a here document (multi-line, unique token)

reuse the last command in current command

sh

!! (then space or tab to expand)

show all environment variables

sh

env

what's &>

sh

redirect both stdout and stderr

loop over a range (e.g. a-z)

sh

for i in {a..z}