Meaning of $? (dollar question mark) in shell scripts What does echo $? mean in shell programming? true echo $? # echoes 0 false echo $? # echoes 1 From the manual: (acessible by calling man bash in your shell) ? Expands to the exit status of the most recently executed foreground pipeline By convention an exit status of 0 means success, and non-zero return status means failure Learn more about exit statuses on wikipedia There are other special
What does $# mean in shell? - Unix Linux Stack Exchange What does $# mean in shell? I have code such as if [ $# -eq 0 ] then I want to understand what $# means, but Google search is very bad for searching these kinds of things
Difference between ${} and $() in a shell script - Super User $(command) is “command substitution” As you seem to understand, it runs the command, captures its output, and inserts that into the command line that contains the $(…); e g , $ ls -ld $(date +%B) txt -rwxr-xr-x 1 Noob Noob 867 Jul 2 11:09 July txt ${parameter} is “parameter substitution” A lot of information can be found in the shell’s man page, bash (1), under the “ Parameter
What is the difference between $@ and $* in shell scripts? In shell scripts, what is the difference between $@ and $*? Which one is the preferred way to get the script arguments? Are there differences between the different shell interpreters about this?
What are the special dollar sign shell variables? - Stack Overflow $! is the PID of the most recent background command $0 is the name of the shell or shell script Most of the above can be found under Special Parameters in the Bash Reference Manual Here are all the environment variables set by the shell For a comprehensive index, please see the Reference Manual Variable Index