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138
votes
15answers
58k views

Get exit status of process that's piped to another

I have two processes foo and bar, connected with a pipe: $ foo | bar bar always exits 0; I'm interested in the exit code of foo. Is there any way to get at it?
10
votes
4answers
4k views

New parent process when the parent process dies

In UNIX, when a parent process disappears, I thought that all child processes reset init as their parent. Is this not correct all the time? Are there any exceptions?
84
votes
4answers
2k views

Can I somehow add a “&& prog2” to an already running prog1?

Most shells provide functions like && and ; to chain the execution of commands in certain ways. But what if a command is already running, can I still somehow add another command to be executed ...
35
votes
4answers
6k views

Is there any UNIX variant on which a child process dies with its parent?

I have been studying the Linux kernel behaviour for quite some time now, and it's always been clear to me that: When a process dies, all its children are given back to the init process (PID 1) ...
29
votes
2answers
6k views

Why does ( echo “”; exit 1) not exit the script?

I have a script, that does not exit when I want it to. An example script with the same error is: #!/bin/bash function bla() { return 1 } bla || ( echo '1' ; exit 1 ) echo '2' I would assume ...
5
votes
2answers
820 views

How do I look up exit codes for applications?

I'm having difficulty locating a comprehensive up-to-date list of error codes from Bash. e.g.: $ udevadm info /dev/sdx; echo Exit code $? Unknown device, --name=, --path=, or absolute path in /dev/ ...
0
votes
3answers
17k views

Bash ping script file for checking host availability

I am trying to write a bash script in a file that would, when run start pinging a host until it becomes available, when the host becomes reachable it runs a command and stops executing, i tried ...
4
votes
2answers
1k views

Removing zombie process from the process table

Can somebody please explain when parent process receives the exit status of a dead child process via wait, who actually reallocates the memory of the child process and removes it from the process ...
3
votes
1answer
2k views

Evaluating the return value of a command line

How do I evaluate or calculate the return value of a command line? For exemple, I count the number of lines with a grep and I want to know if that value is above X. If so, I want to print the number ...
2
votes
2answers
2k views

How to pass data outside process for zenity progress?

Usually this would be a question about how to pass data from a subprocess to a main process, but maybe zenity has some extra quirks so please focus on zenity. Example: #!/bin/sh ( echo "10" ; sleep ...
19
votes
9answers
5k views

How to make sure that a command is not interrupted, even if terminal is closed? [duplicate]

In Linux. Say I want to run a command and it takes too long. I just want to ensure it's done. How?
13
votes
6answers
2k views

Using “reserved” codes for exit status of shell scripts

I recently came across this list of Exit Codes With Special Meanings from the Advanced Bash-Scripting Guide. They refer to these codes as being reserved and recommend that: According to the above ...
13
votes
2answers
691 views

Why does `exit &` not work?

I don't understand why exit & does not work. Why does it not?
4
votes
3answers
742 views

How to write an abort-on-error script without adding `|| exit $?` to every line?

I'm writing a bash script that should exit the error code of the last failed command and not continue execution. This can be achieved by adding a || exit $? everywhere, but is there an easier way, e.g....
2
votes
1answer
486 views

How to have a bash script perform a specific action on errors of _each_ command?

Similarly to set -e performs an exit on "uncaught" $? != 0, I'd like to have this event trigger the execution of another command, e.g. a logger call. How can this be done?
1
vote
3answers
4k views

What return/exit values can I use in bash functions/scripts?

I want to know what return values we can use that will not be mistaken by for ex. SIGINT? ex.: $sleep 10 $#hit ctrl+c $echo $? 130 so I know I must not use anything like return 130 or exit 130 so ...
0
votes
2answers
33 views

Why is the exit status always 0 at the start of a script?

I have a script like this, named judge: #!/bin/bash echo "last exit status is $?" It always outputs "last exit status is 0". Eg: ls -l; judge # correctly reports 0 ls -z; judge # incorrectly ...