Sed Explanation: sed '/./,$!d' file
Could someone please explain this code that deletes all leading blank lines at the top of a file:
sed '/./,$!d' file
I understand that it is a regex, matching only the first character, but then don't understand the ,$!d part. Is this what it's being replaced by, or are they options for the match?
Is this even a search command if it does not start with 's/'...?
Code source (from another question)
sed
edited Dec 15 at 22:22
Rui F Ribeiro
38.9k1479129
asked Nov 17 '16 at 9:44
Emerson Peters
3716
add a comment |
Could someone please explain this code that deletes all leading blank lines at the top of a file:
sed '/./,$!d' file
I understand that it is a regex, matching only the first character, but then don't understand the ,$!d part. Is this what it's being replaced by, or are they options for the match?
Is this even a search command if it does not start with 's/'...?
Code source (from another question)
sed
edited Dec 15 at 22:22
Rui F Ribeiro
38.9k1479129
asked Nov 17 '16 at 9:44
Emerson Peters
3716
add a comment |
Could someone please explain this code that deletes all leading blank lines at the top of a file:
sed '/./,$!d' file
I understand that it is a regex, matching only the first character, but then don't understand the ,$!d part. Is this what it's being replaced by, or are they options for the match?
Is this even a search command if it does not start with 's/'...?
Code source (from another question)
sed
edited Dec 15 at 22:22
Rui F Ribeiro
38.9k1479129
asked Nov 17 '16 at 9:44
Emerson Peters
3716
Could someone please explain this code that deletes all leading blank lines at the top of a file:
sed '/./,$!d' file
I understand that it is a regex, matching only the first character, but then don't understand the ,$!d part. Is this what it's being replaced by, or are they options for the match?
Is this even a search command if it does not start with 's/'...?
Code source (from another question)
sed
sed
edited Dec 15 at 22:22
Rui F Ribeiro
38.9k1479129
asked Nov 17 '16 at 9:44
Emerson Peters
3716
edited Dec 15 at 22:22
Rui F Ribeiro
38.9k1479129
asked Nov 17 '16 at 9:44
Emerson Peters
3716
edited Dec 15 at 22:22
Rui F Ribeiro
38.9k1479129
edited Dec 15 at 22:22
Rui F Ribeiro
38.9k1479129
edited Dec 15 at 22:22
Rui F Ribeiro
38.9k1479129
38.9k1479129
asked Nov 17 '16 at 9:44
Emerson Peters
3716
asked Nov 17 '16 at 9:44
Emerson Peters
3716
asked Nov 17 '16 at 9:44
Emerson Peters
3716
3716
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
sed '/./,$!d'
From the first line which contains a character (blank or not) to the end of the file - negate (which then means from the beginning of the file to the line before the first line which contains a character) - delete.
This deletes leading empty lines, not blank lines. To delete leading blank lines (lines which are empty or contain only whitespace characters) say '/S/,$!d'.
Read "Sed, an introduction and tutorial" at http://www.grymoire.com/Unix/Sed.html. Then read the reference manual at https://www.gnu.org/software/sed/manual/sed.html.
In short:
The general form of a
sedcommand is [selector][negation]command[flags] (square brackets indicate optional parts)The selector, if present, selects the lines on which the command applies
If
!appears it negates the selector, that is, makes the command apply to the lines which do not match the selector.If no selector is present the command applies to all lines.
A selector can select one line (by number) or a set of lines (by regular expression), or the lines between a start line (by number or regular expression) and an end line (by number or regular expression).
In our case the selector is
/./,$which means from the first line found which matches/./(that is, contains at least one character) to the end of the file ($is used as a line number and means the last line in the file).It is negated by
!, so that the command applies to the lines from the beginning of the file to the line before the first line matching/./.The command
ddeletes the selected lines.
answered Nov 17 '16 at 9:50
AlexP
7,0991125
Could you please explain each thing individually?What does the comma do? I know the $ means the end of the string. I'm guessing the ! means the negate? How did it get to the point of defining the "beginning of the file to the line before the first line which contains a character" point?
– Emerson Peters
Nov 17 '16 at 10:01
Are the ,$!d part of the replace section, or are they options like where the g for a global search would go?
– Emerson Peters
Nov 17 '16 at 10:02
I had both of those tabs open, but couldn't find a reference to these options/commands in the table of contents, or through a quick skim, so I didn't know where to look. It looks like I just need a more global understanding of sed first. Thank you for going into detail. I will use this as reference when studying later. :)
– Emerson Peters
Nov 17 '16 at 10:18
add a comment |
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
});
}
});
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%2f323948%2fsed-explanation-sed-d-file%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
sed '/./,$!d'
From the first line which contains a character (blank or not) to the end of the file - negate (which then means from the beginning of the file to the line before the first line which contains a character) - delete.
This deletes leading empty lines, not blank lines. To delete leading blank lines (lines which are empty or contain only whitespace characters) say '/S/,$!d'.
Read "Sed, an introduction and tutorial" at http://www.grymoire.com/Unix/Sed.html. Then read the reference manual at https://www.gnu.org/software/sed/manual/sed.html.
In short:
The general form of a
sedcommand is [selector][negation]command[flags] (square brackets indicate optional parts)The selector, if present, selects the lines on which the command applies
If
!appears it negates the selector, that is, makes the command apply to the lines which do not match the selector.If no selector is present the command applies to all lines.
A selector can select one line (by number) or a set of lines (by regular expression), or the lines between a start line (by number or regular expression) and an end line (by number or regular expression).
In our case the selector is
/./,$which means from the first line found which matches/./(that is, contains at least one character) to the end of the file ($is used as a line number and means the last line in the file).It is negated by
!, so that the command applies to the lines from the beginning of the file to the line before the first line matching/./.The command
ddeletes the selected lines.
answered Nov 17 '16 at 9:50
AlexP
7,0991125
Could you please explain each thing individually?What does the comma do? I know the $ means the end of the string. I'm guessing the ! means the negate? How did it get to the point of defining the "beginning of the file to the line before the first line which contains a character" point?
– Emerson Peters
Nov 17 '16 at 10:01
Are the ,$!d part of the replace section, or are they options like where the g for a global search would go?
– Emerson Peters
Nov 17 '16 at 10:02
I had both of those tabs open, but couldn't find a reference to these options/commands in the table of contents, or through a quick skim, so I didn't know where to look. It looks like I just need a more global understanding of sed first. Thank you for going into detail. I will use this as reference when studying later. :)
– Emerson Peters
Nov 17 '16 at 10:18
add a comment |
sed '/./,$!d'
From the first line which contains a character (blank or not) to the end of the file - negate (which then means from the beginning of the file to the line before the first line which contains a character) - delete.
This deletes leading empty lines, not blank lines. To delete leading blank lines (lines which are empty or contain only whitespace characters) say '/S/,$!d'.
Read "Sed, an introduction and tutorial" at http://www.grymoire.com/Unix/Sed.html. Then read the reference manual at https://www.gnu.org/software/sed/manual/sed.html.
In short:
The general form of a
sedcommand is [selector][negation]command[flags] (square brackets indicate optional parts)The selector, if present, selects the lines on which the command applies
If
!appears it negates the selector, that is, makes the command apply to the lines which do not match the selector.If no selector is present the command applies to all lines.
A selector can select one line (by number) or a set of lines (by regular expression), or the lines between a start line (by number or regular expression) and an end line (by number or regular expression).
In our case the selector is
/./,$which means from the first line found which matches/./(that is, contains at least one character) to the end of the file ($is used as a line number and means the last line in the file).It is negated by
!, so that the command applies to the lines from the beginning of the file to the line before the first line matching/./.The command
ddeletes the selected lines.
answered Nov 17 '16 at 9:50
AlexP
7,0991125
Could you please explain each thing individually?What does the comma do? I know the $ means the end of the string. I'm guessing the ! means the negate? How did it get to the point of defining the "beginning of the file to the line before the first line which contains a character" point?
– Emerson Peters
Nov 17 '16 at 10:01
Are the ,$!d part of the replace section, or are they options like where the g for a global search would go?
– Emerson Peters
Nov 17 '16 at 10:02
I had both of those tabs open, but couldn't find a reference to these options/commands in the table of contents, or through a quick skim, so I didn't know where to look. It looks like I just need a more global understanding of sed first. Thank you for going into detail. I will use this as reference when studying later. :)
– Emerson Peters
Nov 17 '16 at 10:18
add a comment |
sed '/./,$!d'
From the first line which contains a character (blank or not) to the end of the file - negate (which then means from the beginning of the file to the line before the first line which contains a character) - delete.
This deletes leading empty lines, not blank lines. To delete leading blank lines (lines which are empty or contain only whitespace characters) say '/S/,$!d'.
Read "Sed, an introduction and tutorial" at http://www.grymoire.com/Unix/Sed.html. Then read the reference manual at https://www.gnu.org/software/sed/manual/sed.html.
In short:
The general form of a
sedcommand is [selector][negation]command[flags] (square brackets indicate optional parts)The selector, if present, selects the lines on which the command applies
If
!appears it negates the selector, that is, makes the command apply to the lines which do not match the selector.If no selector is present the command applies to all lines.
A selector can select one line (by number) or a set of lines (by regular expression), or the lines between a start line (by number or regular expression) and an end line (by number or regular expression).
In our case the selector is
/./,$which means from the first line found which matches/./(that is, contains at least one character) to the end of the file ($is used as a line number and means the last line in the file).It is negated by
!, so that the command applies to the lines from the beginning of the file to the line before the first line matching/./.The command
ddeletes the selected lines.
answered Nov 17 '16 at 9:50
AlexP
7,0991125
sed '/./,$!d'
From the first line which contains a character (blank or not) to the end of the file - negate (which then means from the beginning of the file to the line before the first line which contains a character) - delete.
This deletes leading empty lines, not blank lines. To delete leading blank lines (lines which are empty or contain only whitespace characters) say '/S/,$!d'.
Read "Sed, an introduction and tutorial" at http://www.grymoire.com/Unix/Sed.html. Then read the reference manual at https://www.gnu.org/software/sed/manual/sed.html.
In short:
The general form of a
sedcommand is [selector][negation]command[flags] (square brackets indicate optional parts)The selector, if present, selects the lines on which the command applies
If
!appears it negates the selector, that is, makes the command apply to the lines which do not match the selector.If no selector is present the command applies to all lines.
A selector can select one line (by number) or a set of lines (by regular expression), or the lines between a start line (by number or regular expression) and an end line (by number or regular expression).
In our case the selector is
/./,$which means from the first line found which matches/./(that is, contains at least one character) to the end of the file ($is used as a line number and means the last line in the file).It is negated by
!, so that the command applies to the lines from the beginning of the file to the line before the first line matching/./.The command
ddeletes the selected lines.
answered Nov 17 '16 at 9:50
AlexP
7,0991125
edited Nov 17 '16 at 10:14
answered Nov 17 '16 at 9:50
AlexP
7,0991125
answered Nov 17 '16 at 9:50
AlexP
7,0991125
answered Nov 17 '16 at 9:50
AlexP
7,0991125
7,0991125
Could you please explain each thing individually?What does the comma do? I know the $ means the end of the string. I'm guessing the ! means the negate? How did it get to the point of defining the "beginning of the file to the line before the first line which contains a character" point?
– Emerson Peters
Nov 17 '16 at 10:01
Are the ,$!d part of the replace section, or are they options like where the g for a global search would go?
– Emerson Peters
Nov 17 '16 at 10:02
I had both of those tabs open, but couldn't find a reference to these options/commands in the table of contents, or through a quick skim, so I didn't know where to look. It looks like I just need a more global understanding of sed first. Thank you for going into detail. I will use this as reference when studying later. :)
– Emerson Peters
Nov 17 '16 at 10:18
add a comment |
Could you please explain each thing individually?What does the comma do? I know the $ means the end of the string. I'm guessing the ! means the negate? How did it get to the point of defining the "beginning of the file to the line before the first line which contains a character" point?
– Emerson Peters
Nov 17 '16 at 10:01
Are the ,$!d part of the replace section, or are they options like where the g for a global search would go?
– Emerson Peters
Nov 17 '16 at 10:02
I had both of those tabs open, but couldn't find a reference to these options/commands in the table of contents, or through a quick skim, so I didn't know where to look. It looks like I just need a more global understanding of sed first. Thank you for going into detail. I will use this as reference when studying later. :)
– Emerson Peters
Nov 17 '16 at 10:18
Could you please explain each thing individually?What does the comma do? I know the $ means the end of the string. I'm guessing the ! means the negate? How did it get to the point of defining the "beginning of the file to the line before the first line which contains a character" point?
– Emerson Peters
Nov 17 '16 at 10:01
Could you please explain each thing individually?What does the comma do? I know the $ means the end of the string. I'm guessing the ! means the negate? How did it get to the point of defining the "beginning of the file to the line before the first line which contains a character" point?
– Emerson Peters
Nov 17 '16 at 10:01
Are the ,$!d part of the replace section, or are they options like where the g for a global search would go?
– Emerson Peters
Nov 17 '16 at 10:02
Are the ,$!d part of the replace section, or are they options like where the g for a global search would go?
– Emerson Peters
Nov 17 '16 at 10:02
I had both of those tabs open, but couldn't find a reference to these options/commands in the table of contents, or through a quick skim, so I didn't know where to look. It looks like I just need a more global understanding of sed first. Thank you for going into detail. I will use this as reference when studying later. :)
– Emerson Peters
Nov 17 '16 at 10:18
I had both of those tabs open, but couldn't find a reference to these options/commands in the table of contents, or through a quick skim, so I didn't know where to look. It looks like I just need a more global understanding of sed first. Thank you for going into detail. I will use this as reference when studying later. :)
– Emerson Peters
Nov 17 '16 at 10:18
add a comment |
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.
Some of your past answers have not been well-received, and you're in danger of being blocked from answering.
Please pay close attention to the following guidance:
- 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%2f323948%2fsed-explanation-sed-d-file%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
