UNIX Command Line

1::catchall for general errors[ miscellaneous errors, such as "divide by zero"]
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$ let "var1 = 1/0"
-bash: let: var1 = 1/0: division by 0 (error token is "0")

$ echo $?
1

2:: misuse of shell builtins, according to Bash documentation [Seldom seen, usually defaults to exit code 1]
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$ ls /tmp/notexi
ls: /tmp/notexi: No such file or directory

$ echo $?
1

126::"command invoked cannot execute" [permission problem or command is not an executable]
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$ ./asd
-bash: ./asd: Permission denied

$ echo $?
126

127:: "command not found" [possible problem with $PATH or a typo]
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$ pks -ef
-bash: pks: command not found

$ echo $?
127


130::"script terminated by Control-C"
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$ sleep 100

(pressed ^C)

$ echo $?
130


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