Bash Tips and Pitfalls
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Tips
Empty a file named filename, keeping the same permission and user/group:
>filename
Print multi-lines text with echo:
$ echo -e "Some text\n...on 2 lines..." # Enable interpretation of backslash escapes (must be quoted!)
Some text
...on 2 lines...
Pits
| Description | Example |
|---|---|
| Space! - Don't forget to add spaces whenever necessary, in particular around brace in function definition, or in test conditions for ifs. |
if -space- [ -space- -f /etc/foo -space- ]; then ... |
| Quote - Always quote parameters, variables passed to test in if ... then ... else: |
if [ "$name" -eq 5 ]; then ... |
| For loops with file - Use simply * to list files in for loops, not `ls *`: |
for file in *; cat "$file"; done # SUCCEEDS, even if white space
for file in `ls *`; cat "$file"; done # FAILS miserably
|
| Space variable setting - There must be no space between the variable name and the subsequent equal sign. Also the variable name must not be prefixed with a $ |
srcDir = $1 # WRONG - spaces around = sign
$srcDir=$1 # WRONG - variable name must not have $ prefix
srcDir=$1 # CORRECT
srcDir="$1" # BEST
|