Difference between revisions of "bash/globbing"
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Commands invoked via bash always, by default, have each of their arguments parsed via the [[glob]] system facility before being passed to the command. | Commands invoked via bash always, by default, have each of their arguments parsed via the [[glob]] system facility before being passed to the command. | ||
| − | == | + | ==Problems== |
This actively interferes with the ability of programs such as [[grep/file masks|grep]] to behave intuitively when given a file-mask spec as input for processing, because: | This actively interferes with the ability of programs such as [[grep/file masks|grep]] to behave intuitively when given a file-mask spec as input for processing, because: | ||
| + | ===wildcard obfuscation=== | ||
* any mask entered will apply only to the current folder. | * any mask entered will apply only to the current folder. | ||
* folders are only included if their names ''also'' match the mask | * folders are only included if their names ''also'' match the mask | ||
** ...thus not being useful as far as being the next layer of folders to search; the program will have to get its own directory listing for that. | ** ...thus not being useful as far as being the next layer of folders to search; the program will have to get its own directory listing for that. | ||
| − | ===Workarounds | + | ===inconsistency=== |
| + | Apparently the file-mask will be passed literally ''if'' no matches are found. (I guess this is useful so the program can say "no matches found for {{arg|filemask}}", but...) | ||
| + | ===ambiguity=== | ||
| + | If there is a file whose name looks like an option because it begins with "-" or "--", and that file matches the file-mask given, the auto-globbing feature will include it verbatim in such a way that the executable may not be able to tell whether it's part of a file-listing or is actually an option from the command-line. | ||
| + | ==Workarounds== | ||
Globbing can be turned off on a per-session basis: | Globbing can be turned off on a per-session basis: | ||
* <code>set -o noglob</code> | * <code>set -o noglob</code> | ||
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* <code>help set</code> | * <code>help set</code> | ||
*: returns more information about bash's <code>set</code> command (the "set" manpage is for something else) | *: returns more information about bash's <code>set</code> command (the "set" manpage is for something else) | ||
| − | + | * Explicitly enclosing the filemask in quotes (double or single) suppresses auto-globbing. <code>bash</code> will strip off the quotes but not parse the contents. | |
| − | + | ==Related== | |
| + | * [[grep/file masks]] | ||
==Links== | ==Links== | ||
* {{l/manpage|glob}} | * {{l/manpage|glob}} | ||
Revision as of 01:01, 18 June 2022
The following notes may apply to other shell environments besides bash, but have only been tested with bash.
Commands invoked via bash always, by default, have each of their arguments parsed via the glob system facility before being passed to the command.
Problems
This actively interferes with the ability of programs such as grep to behave intuitively when given a file-mask spec as input for processing, because:
wildcard obfuscation
- any mask entered will apply only to the current folder.
- folders are only included if their names also match the mask
- ...thus not being useful as far as being the next layer of folders to search; the program will have to get its own directory listing for that.
inconsistency
Apparently the file-mask will be passed literally if no matches are found. (I guess this is useful so the program can say "no matches found for <filemask>", but...)
ambiguity
If there is a file whose name looks like an option because it begins with "-" or "--", and that file matches the file-mask given, the auto-globbing feature will include it verbatim in such a way that the executable may not be able to tell whether it's part of a file-listing or is actually an option from the command-line.
Workarounds
Globbing can be turned off on a per-session basis:
set -o noglob- turns off globbing
- put it in
~/.bashrcto make it the default
set +o noglob- turns globbing back on
help set- returns more information about bash's
setcommand (the "set" manpage is for something else)
- returns more information about bash's
- Explicitly enclosing the filemask in quotes (double or single) suppresses auto-globbing.
bashwill strip off the quotes but not parse the contents.