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syntax:basicgrammar [2015/08/10 03:29]
bill_thomson
syntax:basicgrammar [2019/01/16 01:01]
jdescole
Line 17: Line 17:
 Sounds harder than it actually is. It is what you do daily. You enter simple commands with parameters, and the shell executes them. Sounds harder than it actually is. It is what you do daily. You enter simple commands with parameters, and the shell executes them.
  
-Every complex Bash operationcan ​be split into simple commands:+Every complex Bash operation can be split into simple commands:
 <​code>​ <​code>​
 ls ls
Line 152: Line 152:
 </​code>​ </​code>​
  
-The space between ''​NAME''​ and ''​()''​ is optional, usually you just see it without.+The space between ''​NAME''​ and ''​()''​ is optional, usually you see it without ​the space.
  
-I suggest ​to use the first form. It's specified in POSIX and all Bourne-like shells seem to support it.+I suggest ​using the first form. It's specified in POSIX and all Bourne-like shells seem to support it.
  
-__**Note:​**__ Before version ''​2.05-alpha1'',​ Bash only recognized the definition using curly braces (''​name() { ... }''​), also, other shells allow the definition using **any** command (not only compound command set).+__**Note:​**__ Before version ''​2.05-alpha1'',​ Bash only recognized the definition using curly braces (''​name() { ... }''​),​ other shells allow the definition using **any** command (not just the compound command set).
  
-To execute a function like a regular shell script you would put it together like this:+To execute a function like a regular shell script you put it together like this:
  
 <​code>​ <​code>​
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 mycmd() mycmd()
 { {
-  # this $1 is the one of the function!+  # this $1 belongs to the function!
   find / -iname "​$1"​   find / -iname "​$1"​
 } }
  
-# this $1 is the one of the script itself!+# this $1 belongs ​the script itself!
 mycmd "​$1"​ # Execute command immediately after defining function ​ mycmd "​$1"​ # Execute command immediately after defining function ​
  
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 **Just informational(1):​** **Just informational(1):​**
  
-Internally, for forking, Bash stores ​the function definitions in environment variables. Variables with the content "//() ....//"​.+Internally, for forking, Bash stores function definitions in environment variables. Variables with the content "//() ....//"​.
  
-Something ​like the following works without "​officially"​ declaring a function:+Something ​similar to the following works without "​officially"​ declaring a function:
 <​code>​ <​code>​
 $ export testfn="​() { echo test; }" $ export testfn="​() { echo test; }"
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 **Just informational(2):​** **Just informational(2):​**
  
-It is possible to set function names containing slashes:+It is possible to create ​function names containing slashes:
  
 <​code>​ <​code>​
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 </​code>​ </​code>​
  
-The elements of this name aren't subject to path search, of course.+The elements of this name aren't subject to path search.
  
-The weird names a function ​can have should not be used. Quote from the maintainer:+Weird function ​names should not be used. Quote from the maintainer:
   * //   * //
 It was a mistake to allow such characters in function names (`unset'​ doesn'​t It was a mistake to allow such characters in function names (`unset'​ doesn'​t
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 ===== Grammar summary ===== ===== Grammar summary =====
-Not much of correct definitions,​ just some short **slogans**:​ 
   * a [[basicgrammar#​simple_commands | simple command]] is just a command and its arguments   * a [[basicgrammar#​simple_commands | simple command]] is just a command and its arguments
   * a [[basicgrammar#​pipelines | pipeline]] is one or more [[basicgrammar#​simple_commands | simple command]] probably connected in a pipe   * a [[basicgrammar#​pipelines | pipeline]] is one or more [[basicgrammar#​simple_commands | simple command]] probably connected in a pipe
   * a [[basicgrammar#​lists | list]] is one or more [[basicgrammar#​pipelines | pipelines]] connected by special operators   * a [[basicgrammar#​lists | list]] is one or more [[basicgrammar#​pipelines | pipelines]] connected by special operators
   * a [[basicgrammar#​compound_commands | compound command]] is a [[basicgrammar#​lists | list]] or a special command that forms a new meta-command   * a [[basicgrammar#​compound_commands | compound command]] is a [[basicgrammar#​lists | list]] or a special command that forms a new meta-command
-  * a [[basicgrammar#​shell_function_definitions | function definition]] makes a [[basicgrammar#​compound_commands | compound command]] available under a new name, and in some kind of separate environment+  * a [[basicgrammar#​shell_function_definitions | function definition]] makes a [[basicgrammar#​compound_commands | compound command]] available under a new name, and separate environment
  
  
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 ---- ----
-__A (very ;-)) simple command__+__A (very) simple command__
 <​code>​ <​code>​
 echo "Hello world..."​ echo "Hello world..."​
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 fi fi
 </​code>​ </​code>​
-  * the [[basicgrammar#​compound_commands | compound command]] for the ''​if''​-clause+  * the [[basicgrammar#​compound_commands | compound command]] for the ''​if''​ clause
   * the [[basicgrammar#​lists | list]] that ''​if''​ **checks** actually contains the [[basicgrammar#​simple_commands | simple command]] ''​[ -d /data/mp3 ]''​   * the [[basicgrammar#​lists | list]] that ''​if''​ **checks** actually contains the [[basicgrammar#​simple_commands | simple command]] ''​[ -d /data/mp3 ]''​
   * the [[basicgrammar#​lists | list]] that ''​if''​ **executes** contains a simple command (''​cp mymusic.mp3 /​data/​mp3''​)   * the [[basicgrammar#​lists | list]] that ''​if''​ **executes** contains a simple command (''​cp mymusic.mp3 /​data/​mp3''​)
  
  
-Let'​s ​reverse the exit code of the test command, only one thing changes:+Let'​s ​invert ​test command ​exit code, only one thing changes:
 <​code>​ <​code>​
 if ! [ -d /data/mp3 ]; then if ! [ -d /data/mp3 ]; then
  • syntax/basicgrammar.txt
  • Last modified: 2019/04/01 21:45
  • by ddebhw