Differences
This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision Next revision | Previous revision | ||
|
syntax:pe [2015/12/04 07:15] fgrose [Quote Nesting] decency |
syntax:pe [2019/11/22 19:03] ersen fix expansion offset and length for substring expansion |
||
|---|---|---|---|
| Line 78: | Line 78: | ||
| __Why does the first one fail?__ It prints nothing, because a parameter (variable) named "''WORDs''" is undefined and thus printed as "" (//nothing//). Without using braces for parameter expansion, Bash will interpret the sequence of all valid characters from the introducing "''$''" up to the last valid character as name of the parameter. When using braces you just force Bash to **only interpret the name inside your braces**. | __Why does the first one fail?__ It prints nothing, because a parameter (variable) named "''WORDs''" is undefined and thus printed as "" (//nothing//). Without using braces for parameter expansion, Bash will interpret the sequence of all valid characters from the introducing "''$''" up to the last valid character as name of the parameter. When using braces you just force Bash to **only interpret the name inside your braces**. | ||
| - | Also, please remember, that **parameter names are** (like nearly everything in UNIX(r)) **case sentitive!** | + | Also, please remember, that **parameter names are** (like nearly everything in UNIX(r)) **case sensitive!** |
| The second form with the curly braces is also needed to access positional parameters (arguments to a script) beyond ''$9'': | The second form with the curly braces is also needed to access positional parameters (arguments to a script) beyond ''$9'': | ||
| Line 100: | Line 100: | ||
| ''${!PARAMETER}'' | ''${!PARAMETER}'' | ||
| - | In come cases, like for example | + | In some cases, like for example |
| <code> | <code> | ||
| Line 192: | Line 192: | ||
| * => ''THIS IS SOME TEXT'' | * => ''THIS IS SOME TEXT'' | ||
| * ''echo "${array[2]^^}"'' | * ''echo "${array[2]^^}"'' | ||
| - | * => ''TEXT'' | + | * => ''SOME'' |
| ===== Variable name expansion ===== | ===== Variable name expansion ===== | ||
| Line 325: | Line 325: | ||
| echo ${MYSTRING/%x/y} # RESULT: xxxxxxxxxy</code> | echo ${MYSTRING/%x/y} # RESULT: xxxxxxxxxy</code> | ||
| - | If the replacement part is completely omitted, like, the matches are replaced by the nullstring, i.e. they are removed. This is equivalent to specifying an empty replacement: | + | If the replacement part is completely omitted, the matches are replaced by the nullstring, i.e., they are removed. This is equivalent to specifying an empty replacement: |
| <code> | <code> | ||
| echo ${MYSTRING//conservative/} | echo ${MYSTRING//conservative/} | ||
| Line 392: | Line 392: | ||
| ==== Using only Offset ==== | ==== Using only Offset ==== | ||
| In the first form, the expansion is used without a length value, note that the offset 0 is the first character: | In the first form, the expansion is used without a length value, note that the offset 0 is the first character: | ||
| - | <code>echo ${MYSTRING:34}</code> | + | <code>echo ${MYSTRING:35}</code> |
| => ''<del>Be liberal in what you accept, and </del>conservative in what you send'' | => ''<del>Be liberal in what you accept, and </del>conservative in what you send'' | ||
| ==== Using Offset and Length ==== | ==== Using Offset and Length ==== | ||
| In the second form we also give a length value: | In the second form we also give a length value: | ||
| - | <code>echo ${MYSTRING:34:13}</code> | + | <code>echo ${MYSTRING:35:12}</code> |
| => ''<del>Be liberal in what you accept, and </del>conservative<del> in what you send</del>'' | => ''<del>Be liberal in what you accept, and </del>conservative<del> in what you send</del>'' | ||