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Related to https://github.com/flokoe/bash-hackers-wiki/issues/10
72 lines
1.9 KiB
Markdown
72 lines
1.9 KiB
Markdown
# Grouping commands
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## Synopsis
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{ <LIST>; }
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{
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<LIST>
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}
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## Description
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The [list](../../syntax/basicgrammar.md#lists) `<LIST>` is simply executed in
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the **current** shell environment. The list must be terminated with a
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**newline** or **semicolon**. For parsing reasons, the curly braces must
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be separated from `<LIST>` by a **semicolon** and **blanks** if they\'re
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in the same line! [^1][^2]
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This is known as a **group command**. The return status is the [exit
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status (exit code)](../../scripting/basics.md#exit_codes) of the list.
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The input and output **filedescriptors** are cumulative:
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{
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echo "PASSWD follows"
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cat /etc/passwd
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echo
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echo "GROUPS follows"
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cat /etc/group
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} >output.txt
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This compound command also usually is the body of a [function
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definition](../../syntax/basicgrammar.md#shell_function_definitions), though not
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the only compound command that\'s valid there:
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print_help() {
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echo "Options:"
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echo "-h This help text"
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echo "-f FILE Use config file FILE"
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echo "-u USER Run as user USER"
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}
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## Examples
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### A Try-Catch block
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try_catch() {
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{ # Try-block:
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eval "$@"
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} ||
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{ # Catch-block:
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echo "An error occurred"
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return -1
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}
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}
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## Portability considerations
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## See also
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* [[syntax:ccmd:grouping_subshell | grouping commands in a subshell]]
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[^1]: Actually any properly terminated compound command will work
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without extra separator (also in some other shells), **example**:
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`{ while sleep 1; do echo ZzZzzZ; done }` is valid. But this is not
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documented, infact the documentation explicitly says that a
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semicolon or a newline must separate the enclosed list. \-- thanks
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`geirha` at Freenode
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[^2]: The main reason is the fact that in shell grammar, the curly
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braces are not control operators but reserved words \-- TheBonsai
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