what does '$?' mean in a shell script?

Question

I came across a shell script that contains a statement like,

if [ $val -eq $? ]

What does $? mean here?

Answer 1

$# = number of arguments. Answer is 3.

$@ = what parameters were passed. Answer is 1 2 3.

$? = was last command successful. Answer is 0 which means 'yes'.

Answer 2

I found that the link is very useful and is the great answer. It includes clearly expression with sample.

Answer 3

This is the value of the exit status of the previous command. This is 0 in case of success.

Answer 4

$?

returns the status of the last finished command. Status 0 tells you that everything finished ok.

In addition the $ sign is a special symbol - and in that case $val extract the value that is hold by the variable val

Answer 5

ls *.* or ls would produce the same result. Meaning show zero or more files with any extension in the current directory.

echo $? would display the exit status. If at least one file is displayed from the last command ,the exit status would be zero(success).

Answer 6

What does $? mean here?

$? is the last result of an exit-status ... 0 is by default "successfull"

bash# ls *.*
bash# echo $? 
bash# 0
bash# ls /tmp/not/existing/
bash# echo $?
bash# 2