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bash:cheat [2025-03-21] – dcaibash:cheat [2025-03-21] (current) – dcai
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   * ''%%command 2>>&1%%'': Redirect stderr to stdout   * ''%%command 2>>&1%%'': Redirect stderr to stdout
  
-=== File condition tests ===+=== 💻 File condition tests ===
  
-<code sh>+<code bash>
 if [[ -f filename ]]; then if [[ -f filename ]]; then
-  [...]+  # file exists
 else else
-  [...]+  # file not exists
 fi fi
 +# OR
 +[ -f ~/dotfiles/.bashrc ] && source ~/dotfiles/.bashrc
 </code> </code>
  
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   * file1 ''%%-ot%%'' file2: file1 is older than file2   * file1 ''%%-ot%%'' file2: file1 is older than file2
  
-=== Test last command status code ===+=== 💻 check last command status code ===
  
-<code sh>+<code bash>
 if test $? = 0; then if test $? = 0; then
   echo 'do this';   echo 'do this';
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 </code> </code>
  
-=== Condition tests ===+=== 💻 Variable condition tests ===
  
-<code sh>+<code bash>
 if [[ -z $? ]]; then if [[ -z $? ]]; then
   # last command run successfully   # last command run successfully
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 fi fi
  
-[ -f ~/dotfiles/.bashrc ] && source ~/dotfiles/.bashrc 
-# or 
 [ -z "$ENV_VAR" ] && echo "ENV_VAR is empty" [ -z "$ENV_VAR" ] && echo "ENV_VAR is empty"
 [[ ! -z "$ENV_VAR" ]] && echo "ENV_VAR is not empty" || echo "ENV_VAR is empty" [[ ! -z "$ENV_VAR" ]] && echo "ENV_VAR is not empty" || echo "ENV_VAR is empty"
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   * ''%%string1 !== string2%%'' # string1 is not equal to string2   * ''%%string1 !== string2%%'' # string1 is not equal to string2
  
-== Conditionals ==+=== 💻 numberic conditionals ===
  
   * ''%%-lt%%'': Less than   * ''%%-lt%%'': Less than
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   * ''%%-ne%%'': Not equal to   * ''%%-ne%%'': Not equal to
  
-=== check if command available ===+=== 💻 check if command available ===
  
-<code sh>+<code bash>
 if !type brew &>/dev/null; then if !type brew &>/dev/null; then
   echo "brew install"   echo "brew install"
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 </code> </code>
  
-=== Manipulating and/or expanding variables ===+=== 💻 Manipulating and/or expanding variables ===
  
 [[http://tldp.org/LDP/abs/html/parameter-substitution.html|parameter substitution]] [[http://tldp.org/LDP/abs/html/parameter-substitution.html|parameter substitution]]
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 </code> </code>
  
-=== Shortcuts ===+=== 💻 Shortcuts ===
  
   * CTRL L = Clear the screen   * CTRL L = Clear the screen
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   * !! = repeat last command   * !! = repeat last command
  
-=== For ===+=== 💻 For ===
  
-<code sh>+<code bash>
 for name [in list] for name [in list]
 do do
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 </code> </code>
  
-=== Case ===+=== 💻 Case ===
  
-<code sh>+<code bash>
 case expression in case expression in
   pattern1 )   pattern1 )
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 </code> </code>
  
-=== $() vs backtick ===+=== 💻 $() vs backtick ===
  
 [[http://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xcu_chap02.html#tag_23_02_06_03|ref]] [[http://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xcu_chap02.html#tag_23_02_06_03|ref]]
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 The backticks/gravemarks have been deprecated in favor of ''%%$()%%'' for command substitution. The backticks/gravemarks have been deprecated in favor of ''%%$()%%'' for command substitution.
  
-=== Special bash variables ===+=== 💻 Special bash variables ===
  
 [[http://www.tldp.org/LDP/Bash-Beginners-Guide/html/sect_03_02.html#table_03_03|ref]] [[http://www.tldp.org/LDP/Bash-Beginners-Guide/html/sect_03_02.html#table_03_03|ref]]
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 > The implementation of ''%%$*%%'' has always been a problem and realistically should have been replaced with the behavior of ''%%$@%%''. In almost every case where coders use ''%%$*%%'', they mean ''%%$@%%''. ''%%$*%%'' Can cause bugs and even security holes in your software. > The implementation of ''%%$*%%'' has always been a problem and realistically should have been replaced with the behavior of ''%%$@%%''. In almost every case where coders use ''%%$*%%'', they mean ''%%$@%%''. ''%%$*%%'' Can cause bugs and even security holes in your software.
  
-=== Search ===+=== 💻 Search ===
  
-<code sh>+<code bash>
 find . -iname "*filename*" find . -iname "*filename*"
 find . -type d find . -type d
 </code> </code>
  
bash/cheat.1742553192.txt.gz · Last modified: by dcai

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