Avoid bash if you can and use for example python. Reason is that the bash scripts cannot grow into a larger program, because debugging and crazy syntax.
But sometimes you will encounter bash.
Error Handling with Or Operator “||”
# I usually set these options.
# The -e option causes bash to exit immediately if any command exits with a non-zero status.
# The -x option prints every command before it is executed to simulate debugging.
# The -u option causes bash to exit immediately if any unset variable is used.
set -eux
echo "before";
{
echo "inner";
# This will cause exit from the function.
false;
echo "we will never get here";
} || echo failed
echo "continue here";
# This will cause exit.
false;
echo "We will never get here :(";
Careful with the Star Expansion!
Remember .* expands also to .., which is outer directory!
Listen to The Output of an Already Running Process
The process needs not to have its output piped to a file or other pipe. You can access the output via the proc filesystem:
cat /proc/<pid>/fd/1.
Example:
echo "while true; do sleep 1; echo here; done;" > test.sh;
nohup bash test.sh &
# prints: [1] 1020383
cat /proc/1020383/fd/1;
For stderr use 2 instead of 1:
cat /proc/<pid>/fd/2
Because:
- 0: stdin
- 1: stdout
- 2: stderr
How to Export All Variables From an Env File
Avoid manual exporting with allexport option.
All variables that will be newly defined variables will be exported for use in executed commands.
Example:
set -o allexport
source .env
set +o allexport
Other Sources
- TODO
Good luck!
