147 lines
3.1 KiB
Markdown
147 lines
3.1 KiB
Markdown
---
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title: Signals
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TARGET DECK: Obsidian::STEM
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FILE TAGS: posix::signal
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tags:
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- posix
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- signal
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---
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## Overview
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This is an overview of specific POSIX signals.
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Code | Name
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----- | --------------
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1 | SIGHUP
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2 | SIGINT
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4 | SIGILL
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6 | SIGABRT
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7 | SIGBUS
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8 | SIGFPE
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9 | SIGKILL
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11 | SIGSEGV
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13 | SIGPIPE
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15 | SIGTERM
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## Details
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%%ANKI
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Basic
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What command can we run to access the official manual page for signals?
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Back: `man 7 signal`
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Reference: Dowling, “A List of Signals and What They Mean.”
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Tags: linux::cli
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<!--ID: 1706668253908-->
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END%%
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### SIGHUP (1)
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A process receives a `SIGHUP` signal when the terminal it is attached to goes away before it finishes executing.
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%%ANKI
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Cloze
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Signal {`SIGHUP`} corresponds to number {1}.
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Reference: Dowling, “A List of Signals and What They Mean.”
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<!--ID: 1706668531417-->
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END%%
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%%ANKI
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Basic
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What is the `HUP` in `SIGHUP` an acronym for?
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Back: **H**ang **up**
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Reference: Dowling, “A List of Signals and What They Mean.”
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<!--ID: 1706669687254-->
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END%%
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%%ANKI
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Basic
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When does a process receive a `SIGHUP` signal?
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Back: When the terminal it is attached to disappears before it finishes execution.
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Reference: Dowling, “A List of Signals and What They Mean.”
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<!--ID: 1706669687261-->
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END%%
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%%ANKI
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Basic
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What historical context led to `SIGHUP`'s name?
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Back: This name refers to hanging up the telephone in the days of telephone modems.
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Reference: Dowling, “A List of Signals and What They Mean.”
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<!--ID: 1706669687266-->
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END%%
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%%ANKI
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Basic
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What command is used to make a program immune to `SIGHUP` signals?
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Back: `nohup`
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Reference: `man 1 nohup`
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Tags: linux::cli
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<!--ID: 1706670390877-->
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END%%
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%%ANKI
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Basic
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If a `nohup` program's `stdin` is a terminal, where is its input redirected from?
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Back: An unreadable file.
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Reference: `man 1 nohup`
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Tags: linux::cli
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<!--ID: 1706670390904-->
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END%%
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%%ANKI
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Basic
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If a `nohup` program's `stdout` is a terminal, where is its output redirected to?
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Back: `nohup.out` if possible, `$HOME/nohup.out` otherwise.
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Reference: `man 1 nohup`
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Tags: linux::cli
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<!--ID: 1706670390909-->
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END%%
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%%ANKI
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Basic
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If a `nohup` program's `stderr` is a terminal, where is its errors redirected to?
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Back: `stdout`
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Reference: `man 1 nohup`
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Tags: linux::cli
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<!--ID: 1706670390913-->
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END%%
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%%ANKI
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Basic
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What command can be run to view all processes that would receive a `SIGHUP` when the current terminal exits?
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Back: `ps T`
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Reference: `man 1 ps`
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<!--ID: 1706670390919-->
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END%%
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### SIGINT (2)
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Indicates the process was interrupted by the user. Happens when pressing `Ctrl-C` from the controlling terminal.
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%%ANKI
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Cloze
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Signal {`SIGINT`} corresponds to number {2}.
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Reference: Dowling, “A List of Signals and What They Mean.”
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<!--ID: 1706815743860-->
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END%%
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%%ANKI
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Basic
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What control sequence usually triggers a `SIGINT`?
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Back: `Ctrl-C`
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Reference: Dowling, “A List of Signals and What They Mean.”
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<!--ID: 1706815743867-->
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END%%
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%%ANKI
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Basic
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What is the `INT` in `SIGINT` short for?
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Back: **Int**errupt
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Reference: Dowling, “A List of Signals and What They Mean.”
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<!--ID: 1706815743870-->
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END%%
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## References
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* Dowling, “A List of Signals and What They Mean.”
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