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56 lines
2.0 KiB
Plaintext
56 lines
2.0 KiB
Plaintext
====== Grouping commands ======
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===== Synopsis =====
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<code>{ <LIST>; }</code>
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<code>
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{
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<LIST>
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}
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</code>
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===== Description =====
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The [[syntax:basicgrammar#lists|list]] ''<LIST>'' is simply executed in the **current** shell environment. The list must be terminated with a **newline** or **semicolon**. For parsing reasons, the curly braces must be separated from ''<LIST>'' by a **semicolon** and **blanks** if they're in the same line! ((Actually any properly terminated compound command will work without extra separator (also in some other shells), **example**: ''{ while sleep 1; do echo ZzZzzZ; done }'' is valid. But this is not documented, infact the documentation explicitly says that a semicolon or a newline must separate the enclosed list. -- thanks ''geirha'' at Freenode))((The main reason is the fact that in shell grammar, the curly braces are not control operators but reserved words -- TheBonsai))
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This is known as a **group command**. The return status is the [[scripting:basics#exit_codes|exit status (exit code)]] of the list.
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The input and output **filedescriptors** are cumulative:
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<code>
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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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</code>
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This compound command also usually is the body of a [[syntax:basicgrammar#shell_function_definitions | function definition]], though not the only compound command that's valid there:
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<code>
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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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</code>
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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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