How is the wildcard * interpreted as a command?
I know how * is interpreted in commands like ls for example. But when trying to run * as a command the shell tries to execute the first file or directory in your working directory. Why is this? How does the shell understand *?
bash wildcards
edited 8 hours ago
Glorfindel
2991411
asked 9 hours ago
osmakosmak
183
New contributor
osmak is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
I know how * is interpreted in commands like ls for example. But when trying to run * as a command the shell tries to execute the first file or directory in your working directory. Why is this? How does the shell understand *?
bash wildcards
edited 8 hours ago
Glorfindel
2991411
asked 9 hours ago
osmakosmak
183
New contributor
osmak is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
I know how * is interpreted in commands like ls for example. But when trying to run * as a command the shell tries to execute the first file or directory in your working directory. Why is this? How does the shell understand *?
bash wildcards
edited 8 hours ago
Glorfindel
2991411
asked 9 hours ago
osmakosmak
183
New contributor
osmak is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
I know how * is interpreted in commands like ls for example. But when trying to run * as a command the shell tries to execute the first file or directory in your working directory. Why is this? How does the shell understand *?
bash wildcards
bash wildcards
edited 8 hours ago
Glorfindel
2991411
asked 9 hours ago
osmakosmak
183
New contributor
osmak is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 8 hours ago
Glorfindel
2991411
asked 9 hours ago
osmakosmak
183
New contributor
osmak is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 8 hours ago
Glorfindel
2991411
edited 8 hours ago
Glorfindel
2991411
edited 8 hours ago
Glorfindel
2991411
2991411
asked 9 hours ago
osmakosmak
183
New contributor
osmak is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 9 hours ago
osmakosmak
183
asked 9 hours ago
osmakosmak
183
183
New contributor
osmak is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
osmak is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
osmak is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
Unlike in some other operating systems, in Unixes, it's the shell that expands filename wildcards. It expands parameter expansions and globs first, then uses the (now) first word as the name for the command to run.
This is also why files named with a leading dash can be troublesome: a glob like * will expand to the file names, and a name starting with a dash may be taken as an option. (The scary example being that a file called -r in the working directory would make rm * remove everything recursively...)
Usually, one wouldn't use * as the first item on any command line, though, so having the first file determine the command to run in that case isn't likely to cause problems.
edited 6 hours ago
DarkHeart
3,52632340
answered 9 hours ago
ilkkachuilkkachu
60.9k1098174
1
I think this example misses an important point out, that filename expansion is not subject to further field splitting, unlike parameter expansion, so filenames with spaces are still safe.
– Michael Homer
9 hours ago
OK, so I think I misunderstood how the * work in the first place. I thought that it is a common syntax used in Linux commands. But, if I understood your answer correctly, then filename expansion is a shell feature not a command feature. So what happened is that * got replaced by all file or directory names in PWD but when the shell tried executing the first one it produced the error I saw.
– osmak
9 hours ago
@osmak, yeah, it's a shell feature on Unixes. Easier that way, so each and every program doesn't have to implement it. Though of course programs likefindknow how to expand similar patterns, too (e.g.file -name "*.txt")
– ilkkachu
8 hours ago
@osmak That is a correct understanding.
– Kusalananda
8 hours ago
2
A file named-ris bad, but one named-rfis even worse.
– Monty Harder
6 hours ago
|
show 4 more comments
Your Answer
StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "106"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});
function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});
}
});
osmak is a new contributor. Be nice, and check out our Code of Conduct.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f505707%2fhow-is-the-wildcard-interpreted-as-a-command%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
Unlike in some other operating systems, in Unixes, it's the shell that expands filename wildcards. It expands parameter expansions and globs first, then uses the (now) first word as the name for the command to run.
This is also why files named with a leading dash can be troublesome: a glob like * will expand to the file names, and a name starting with a dash may be taken as an option. (The scary example being that a file called -r in the working directory would make rm * remove everything recursively...)
Usually, one wouldn't use * as the first item on any command line, though, so having the first file determine the command to run in that case isn't likely to cause problems.
edited 6 hours ago
DarkHeart
3,52632340
answered 9 hours ago
ilkkachuilkkachu
60.9k1098174
1
I think this example misses an important point out, that filename expansion is not subject to further field splitting, unlike parameter expansion, so filenames with spaces are still safe.
– Michael Homer
9 hours ago
OK, so I think I misunderstood how the * work in the first place. I thought that it is a common syntax used in Linux commands. But, if I understood your answer correctly, then filename expansion is a shell feature not a command feature. So what happened is that * got replaced by all file or directory names in PWD but when the shell tried executing the first one it produced the error I saw.
– osmak
9 hours ago
@osmak, yeah, it's a shell feature on Unixes. Easier that way, so each and every program doesn't have to implement it. Though of course programs likefindknow how to expand similar patterns, too (e.g.file -name "*.txt")
– ilkkachu
8 hours ago
@osmak That is a correct understanding.
– Kusalananda
8 hours ago
2
A file named-ris bad, but one named-rfis even worse.
– Monty Harder
6 hours ago
|
show 4 more comments
Unlike in some other operating systems, in Unixes, it's the shell that expands filename wildcards. It expands parameter expansions and globs first, then uses the (now) first word as the name for the command to run.
This is also why files named with a leading dash can be troublesome: a glob like * will expand to the file names, and a name starting with a dash may be taken as an option. (The scary example being that a file called -r in the working directory would make rm * remove everything recursively...)
Usually, one wouldn't use * as the first item on any command line, though, so having the first file determine the command to run in that case isn't likely to cause problems.
edited 6 hours ago
DarkHeart
3,52632340
answered 9 hours ago
ilkkachuilkkachu
60.9k1098174
1
I think this example misses an important point out, that filename expansion is not subject to further field splitting, unlike parameter expansion, so filenames with spaces are still safe.
– Michael Homer
9 hours ago
OK, so I think I misunderstood how the * work in the first place. I thought that it is a common syntax used in Linux commands. But, if I understood your answer correctly, then filename expansion is a shell feature not a command feature. So what happened is that * got replaced by all file or directory names in PWD but when the shell tried executing the first one it produced the error I saw.
– osmak
9 hours ago
@osmak, yeah, it's a shell feature on Unixes. Easier that way, so each and every program doesn't have to implement it. Though of course programs likefindknow how to expand similar patterns, too (e.g.file -name "*.txt")
– ilkkachu
8 hours ago
@osmak That is a correct understanding.
– Kusalananda
8 hours ago
2
A file named-ris bad, but one named-rfis even worse.
– Monty Harder
6 hours ago
|
show 4 more comments
Unlike in some other operating systems, in Unixes, it's the shell that expands filename wildcards. It expands parameter expansions and globs first, then uses the (now) first word as the name for the command to run.
This is also why files named with a leading dash can be troublesome: a glob like * will expand to the file names, and a name starting with a dash may be taken as an option. (The scary example being that a file called -r in the working directory would make rm * remove everything recursively...)
Usually, one wouldn't use * as the first item on any command line, though, so having the first file determine the command to run in that case isn't likely to cause problems.
edited 6 hours ago
DarkHeart
3,52632340
answered 9 hours ago
ilkkachuilkkachu
60.9k1098174
Unlike in some other operating systems, in Unixes, it's the shell that expands filename wildcards. It expands parameter expansions and globs first, then uses the (now) first word as the name for the command to run.
This is also why files named with a leading dash can be troublesome: a glob like * will expand to the file names, and a name starting with a dash may be taken as an option. (The scary example being that a file called -r in the working directory would make rm * remove everything recursively...)
Usually, one wouldn't use * as the first item on any command line, though, so having the first file determine the command to run in that case isn't likely to cause problems.
edited 6 hours ago
DarkHeart
3,52632340
answered 9 hours ago
ilkkachuilkkachu
60.9k1098174
edited 6 hours ago
DarkHeart
3,52632340
edited 6 hours ago
DarkHeart
3,52632340
edited 6 hours ago
DarkHeart
3,52632340
3,52632340
answered 9 hours ago
ilkkachuilkkachu
60.9k1098174
answered 9 hours ago
ilkkachuilkkachu
60.9k1098174
answered 9 hours ago
ilkkachuilkkachu
60.9k1098174
60.9k1098174
1
I think this example misses an important point out, that filename expansion is not subject to further field splitting, unlike parameter expansion, so filenames with spaces are still safe.
– Michael Homer
9 hours ago
OK, so I think I misunderstood how the * work in the first place. I thought that it is a common syntax used in Linux commands. But, if I understood your answer correctly, then filename expansion is a shell feature not a command feature. So what happened is that * got replaced by all file or directory names in PWD but when the shell tried executing the first one it produced the error I saw.
– osmak
9 hours ago
@osmak, yeah, it's a shell feature on Unixes. Easier that way, so each and every program doesn't have to implement it. Though of course programs likefindknow how to expand similar patterns, too (e.g.file -name "*.txt")
– ilkkachu
8 hours ago
@osmak That is a correct understanding.
– Kusalananda
8 hours ago
2
A file named-ris bad, but one named-rfis even worse.
– Monty Harder
6 hours ago
|
show 4 more comments
1
I think this example misses an important point out, that filename expansion is not subject to further field splitting, unlike parameter expansion, so filenames with spaces are still safe.
– Michael Homer
9 hours ago
OK, so I think I misunderstood how the * work in the first place. I thought that it is a common syntax used in Linux commands. But, if I understood your answer correctly, then filename expansion is a shell feature not a command feature. So what happened is that * got replaced by all file or directory names in PWD but when the shell tried executing the first one it produced the error I saw.
– osmak
9 hours ago
@osmak, yeah, it's a shell feature on Unixes. Easier that way, so each and every program doesn't have to implement it. Though of course programs likefindknow how to expand similar patterns, too (e.g.file -name "*.txt")
– ilkkachu
8 hours ago
@osmak That is a correct understanding.
– Kusalananda
8 hours ago
2
A file named-ris bad, but one named-rfis even worse.
– Monty Harder
6 hours ago
1
1
I think this example misses an important point out, that filename expansion is not subject to further field splitting, unlike parameter expansion, so filenames with spaces are still safe.
– Michael Homer
9 hours ago
I think this example misses an important point out, that filename expansion is not subject to further field splitting, unlike parameter expansion, so filenames with spaces are still safe.
– Michael Homer
9 hours ago
OK, so I think I misunderstood how the * work in the first place. I thought that it is a common syntax used in Linux commands. But, if I understood your answer correctly, then filename expansion is a shell feature not a command feature. So what happened is that * got replaced by all file or directory names in PWD but when the shell tried executing the first one it produced the error I saw.
– osmak
9 hours ago
OK, so I think I misunderstood how the * work in the first place. I thought that it is a common syntax used in Linux commands. But, if I understood your answer correctly, then filename expansion is a shell feature not a command feature. So what happened is that * got replaced by all file or directory names in PWD but when the shell tried executing the first one it produced the error I saw.
– osmak
9 hours ago
@osmak, yeah, it's a shell feature on Unixes. Easier that way, so each and every program doesn't have to implement it. Though of course programs like
find know how to expand similar patterns, too (e.g. file -name "*.txt")– ilkkachu
8 hours ago
@osmak, yeah, it's a shell feature on Unixes. Easier that way, so each and every program doesn't have to implement it. Though of course programs like
find know how to expand similar patterns, too (e.g. file -name "*.txt")– ilkkachu
8 hours ago
@osmak That is a correct understanding.
– Kusalananda
8 hours ago
@osmak That is a correct understanding.
– Kusalananda
8 hours ago
2
2
A file named
-r is bad, but one named -rf is even worse.– Monty Harder
6 hours ago
A file named
-r is bad, but one named -rf is even worse.– Monty Harder
6 hours ago
|
show 4 more comments
osmak is a new contributor. Be nice, and check out our Code of Conduct.
osmak is a new contributor. Be nice, and check out our Code of Conduct.
osmak is a new contributor. Be nice, and check out our Code of Conduct.
osmak is a new contributor. Be nice, and check out our Code of Conduct.
Thanks for contributing an answer to Unix & Linux Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f505707%2fhow-is-the-wildcard-interpreted-as-a-command%23new-answer', 'question_page');
}
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
