I'm trying to temporarily disable dhcp on all connections in a computer using bash, so I need the process to be reversible. My approach is to comment out lines that contain BOOTPROTO=dhcp, and then insert a line below it with BOOTPROTO=none. I'm not sure of the correct syntax to make sed understand the line number stored in the $insertLine variable.
fileList=$(ls /etc/sysconfig/network-scripts | grep ^ifcfg)
path="/etc/sysconfig/network-scripts/"
for file in $fileList
do
echo "looking for dhcp entry in $file"
if [ $(cat $path$file | grep ^BOOTPROTO=dhcp) ]; then
echo "disabling dhcp in $file"
editLine=$(grep -n ^BOOTPROTO=dhcp /$path$file | cut -d : -f 1 )
#comment out the original dhcp value
sed -i "s/BOOTPROTO=dhcp/#BOOTPROTO=dhcp/g" $path$file
#insert a line below it with value of none.
((insertLine=$editLine+1))
sed "$($insertLine)iBOOTPROTO=none" $path$file
fi
done
Any help using sed or other stream editor greatly appreciated. I'm using RHEL 6.
The sed editor should be able to do the job, without having to to be combine bash, grep, cat, etc. Easier to test, and more reliable.
The whole scripts can be simplified to the below. It performs all operations (substitution and the insert) with a single pass using multiple sed scriptlets.
#! /bin/sh
for file in $(grep -l "^BOOTPROTO=dhcp" /etc/sysconfig/network-scripts/ifcfg*) ; do
sed -i -e "s/BOOTPROTO=dhcp/#BOOTPROTO=dhcp/g" -e "/BOOTPROTO=dhcp/i BOOTPROTO=none" $file
done
As side note consider NOT using path as variable to avoid possible confusion with the 'PATH` environment variable.
Writing it up, your attempt with the following fails:
sed "$($insertLine)iBOOTPROTO=none" $path$file
because:
$($insertLine) encloses $insertLIne in a command substitution which when $insertLIne is evaluated it returns a number which is not a command generating an error.
your call to sed does not include the -i option to edit the file $path$file in place.
You can correct the issues with:
sed -i "${insertLine}i BOOTPROTO=none" $path$file
Which is just sed - i (edit in place) and Ni where N is the number of the line to insert followed by the content to insert and finally what file to insert it in. You add ${..} to insertLine to protect the variable name from the i that follows and then the expression is double-quoted to allow variable expansion.
Let me know if you have any further questions.
(and see dash-o's answer for refactoring the whole thing to simply use sed to make the change without spawning 10 other subshells)
This might be very simple but I am stuck at getting this done in shell/bash.
I have input like "a/b/c/d" and I want to replace all '/' with '\/' and the output would be 'a/b/c/d'
another example is 12.12.12.12/32 >>> 12.12.12.12\/32
Any help would be appreciated.
You can use bash's parameter expansion:
$ input="a/b/c/d"
$ echo "${input//\//\\/}"
a\/b\/c\/d
Given a variable input, ${input//xxx/yyy} yields the content of input with every xxx replaced with yyy. Here xxx is \/ (/ must be escaped to not be mixed up with the next /) and yyy is \\/ (\/ with \ being escaped).
Using bash only
var='a/b/c/d'
echo "${var//\//\\/}"
This would do:
echo "12.12.12.12/32" |sed 's,/,\\/,g'
Output:
12.12.12.12\/32
In such scenarios, use a delimiter other than /, as i used , in the above example. You can use for example: #,?....etc
Depending on how you access the text or strings you want to make the replacement in, something like this might work. You have to escape both / and \ inside the sed command.
var='a/b/c/d'
echo "$var" | sed 's/\//\\\//g'
might be an easy question, I'm new in bash and haven't been able to find the solution to my question.
I'm writing the following script:
for file in `ls *.map`; do
ID=${file%.map}
convertf -p ${ID}_par #this is a program that I use, no problem
NAME=head -n 1 ${ID}.ind | cut -f1 -d":" #Now: This step is the problem: don't seem to be able to make a proper NAME function. I just want to take the first column of the first line of the file ${ID}.ind
It gives me the return
line 5: bad substitution
any help?
Thanks!
There are a couple of issues in your code:
for file in `ls *.map` does not do what you want. It will fail e.g. if any of the filenames contains a space or *, but there's more. See http://mywiki.wooledge.org/BashPitfalls#for_i_in_.24.28ls_.2A.mp3.29 for details.
You should just use for file in *.map instead.
ALL_UPPERCASE names are generally used for system variables and built-in shell variables. Use lowercase for your own names.
That said,
for file in *.map; do
id="${file%.map}"
convertf -p "${id}_par"
name="$(head -n 1 "${id}.ind" | cut -f1 -d":")"
...
looks like it would work. We just use $( cmd ) to capture the output of a command in a string.
I want to trim a pathname beyond a certain point after finding a keyword. I'm drawing a blank this morning.
/home/quikq/1.0/dev/Java/tsupdater/src/tsupdater.java
I want to find the keyword Java, save the pathname beyond that (tsupdater), then cut everything off after the Java portion.
I don't know if this is what you want, but you can split the pathname into two with:
echo "/home/quikq/1.0/dev/Java/tsupdater/src/tsupdater.java" | sed 'h;s/.*Java//p;g;s/Java.*/Java/'
Which outputs:
/tsupdater/src/tsupdater.java
/home/quikq/1.0/dev/Java
If you would like to save the second part into a file part2.txt and print the first part, you could do:
echo "/home/quikq/1.0/dev/Java/tsupdater/src/tsupdater.java" | sed 'h;s/.*Java//;wpart2.txt;g;s/Java.*/Java/'
If you're writing a shell script:
myvar="/home/quikq/1.0/dev/Java/tsupdater/src/tsupdater.java"
part1="${myvar%Java*}Java"
part2="${myvar#*Java/}"
Hope this helps =)
take one you need:
kent$ echo "/home/quikq/1.0/dev/Java/tsupdater/src/tsupdater.java"|sed -r 's#(.*Java/[^/]*).*#\1#g'
/home/quikq/1.0/dev/Java/tsupdater
kent$ echo "/home/quikq/1.0/dev/Java/tsupdater/src/tsupdater.java"|sed -r 's#(.*Java).*#\1#g'
/home/quikq/1.0/dev/Java
kent$ echo "/home/quikq/1.0/dev/Java/tsupdater/src/tsupdater.java"|sed -r 's#.*Java/([^/]*).*#\1#g'
tsupdater
I'm not entirely sure what you want as output (please specify more clearly), but this command:
echo "/home/quikq/1.0/dev/Java/tsupdater/src/tsupdater.java" | sed 's/.*Java//'
results in:
/tsupdater/src/tsupdater.java
If you want the preceding part then this command:
echo "/home/quikq/1.0/dev/Java/tsupdater/src/tsupdater.java" | sed 's/Java.*//'
results in:
/home/quikq/1.0/dev/
Like I said, I was having a weird morning, but it dawned on me.
echo /home/quikq/1.0/dev/Java/TSUpdater/src/TSUpdater.java | sed s/Java.*//g
Yields
/home/quikq/1.0/dev
Lots of great tips here for chopping it up different ways though. Thanks a bunch!
Objective
Change these filenames:
F00001-0708-RG-biasliuyda
F00001-0708-CS-akgdlaul
F00001-0708-VF-hioulgigl
to these filenames:
F0001-0708-RG-biasliuyda
F0001-0708-CS-akgdlaul
F0001-0708-VF-hioulgigl
Shell Code
To test:
ls F00001-0708-*|sed 's/\(.\).\(.*\)/mv & \1\2/'
To perform:
ls F00001-0708-*|sed 's/\(.\).\(.*\)/mv & \1\2/' | sh
My Question
I don't understand the sed code. I understand what the substitution
command
$ sed 's/something/mv'
means. And I understand regular expressions somewhat. But I don't
understand what's happening here:
\(.\).\(.*\)
or here:
& \1\2/
The former, to me, just looks like it means: "a single character,
followed by a single character, followed by any length sequence of a
single character"--but surely there's more to it than that. As far as
the latter part:
& \1\2/
I have no idea.
First, I should say that the easiest way to do this is to use the
prename or rename commands.
On Ubuntu, OSX (Homebrew package rename, MacPorts package p5-file-rename), or other systems with perl rename (prename):
rename s/0000/000/ F0000*
or on systems with rename from util-linux-ng, such as RHEL:
rename 0000 000 F0000*
That's a lot more understandable than the equivalent sed command.
But as for understanding the sed command, the sed manpage is helpful. If
you run man sed and search for & (using the / command to search),
you'll find it's a special character in s/foo/bar/ replacements.
s/regexp/replacement/
Attempt to match regexp against the pattern space. If success‐
ful, replace that portion matched with replacement. The
replacement may contain the special character & to refer to that
portion of the pattern space which matched, and the special
escapes \1 through \9 to refer to the corresponding matching
sub-expressions in the regexp.
Therefore, \(.\) matches the first character, which can be referenced by \1.
Then . matches the next character, which is always 0.
Then \(.*\) matches the rest of the filename, which can be referenced by \2.
The replacement string puts it all together using & (the original
filename) and \1\2 which is every part of the filename except the 2nd
character, which was a 0.
This is a pretty cryptic way to do this, IMHO. If for
some reason the rename command was not available and you wanted to use
sed to do the rename (or perhaps you were doing something too complex
for rename?), being more explicit in your regex would make it much
more readable. Perhaps something like:
ls F00001-0708-*|sed 's/F0000\(.*\)/mv & F000\1/' | sh
Being able to see what's actually changing in the
s/search/replacement/ makes it much more readable. Also it won't keep
sucking characters out of your filename if you accidentally run it
twice or something.
you've had your sed explanation, now you can use just the shell, no need external commands
for file in F0000*
do
echo mv "$file" "${file/#F0000/F000}"
# ${file/#F0000/F000} means replace the pattern that starts at beginning of string
done
I wrote a small post with examples on batch renaming using sed couple of years ago:
http://www.guyrutenberg.com/2009/01/12/batch-renaming-using-sed/
For example:
for i in *; do
mv "$i" "`echo $i | sed "s/regex/replace_text/"`";
done
If the regex contains groups (e.g. \(subregex\) then you can use them in the replacement text as \1\,\2 etc.
The easiest way would be:
for i in F00001*; do mv "$i" "${i/F00001/F0001}"; done
or, portably,
for i in F00001*; do mv "$i" "F0001${i#F00001}"; done
This replaces the F00001 prefix in the filenames with F0001.
credits to mahesh here: http://www.debian-administration.org/articles/150
The sed command
s/\(.\).\(.*\)/mv & \1\2/
means to replace:
\(.\).\(.*\)
with:
mv & \1\2
just like a regular sed command. However, the parentheses, & and \n markers change it a little.
The search string matches (and remembers as pattern 1) the single character at the start, followed by a single character, follwed by the rest of the string (remembered as pattern 2).
In the replacement string, you can refer to these matched patterns to use them as part of the replacement. You can also refer to the whole matched portion as &.
So what that sed command is doing is creating a mv command based on the original file (for the source) and character 1 and 3 onwards, effectively removing character 2 (for the destination). It will give you a series of lines along the following format:
mv F00001-0708-RG-biasliuyda F0001-0708-RG-biasliuyda
mv abcdef acdef
and so on.
Using perl rename (a must have in the toolbox):
rename -n 's/0000/000/' F0000*
Remove -n switch when the output looks good to rename for real.
There are other tools with the same name which may or may not be able to do this, so be careful.
The rename command that is part of the util-linux package, won't.
If you run the following command (GNU)
$ rename
and you see perlexpr, then this seems to be the right tool.
If not, to make it the default (usually already the case) on Debian and derivative like Ubuntu :
$ sudo apt install rename
$ sudo update-alternatives --set rename /usr/bin/file-rename
For archlinux:
pacman -S perl-rename
For RedHat-family distros:
yum install prename
The 'prename' package is in the EPEL repository.
For Gentoo:
emerge dev-perl/rename
For *BSD:
pkg install gprename
or p5-File-Rename
For Mac users:
brew install rename
If you don't have this command with another distro, search your package manager to install it or do it manually:
cpan -i File::Rename
Old standalone version can be found here
man rename
This tool was originally written by Larry Wall, the Perl's dad.
The backslash-paren stuff means, "while matching the pattern, hold on to the stuff that matches in here." Later, on the replacement text side, you can get those remembered fragments back with "\1" (first parenthesized block), "\2" (second block), and so on.
If all you're really doing is removing the second character, regardless of what it is, you can do this:
s/.//2
but your command is building a mv command and piping it to the shell for execution.
This is no more readable than your version:
find -type f | sed -n 'h;s/.//4;x;s/^/mv /;G;s/\n/ /g;p' | sh
The fourth character is removed because find is prepending each filename with "./".
Here's what I would do:
for file in *.[Jj][Pp][Gg] ;do
echo mv -vi \"$file\" `jhead $file|
grep Date|
cut -b 16-|
sed -e 's/:/-/g' -e 's/ /_/g' -e 's/$/.jpg/g'` ;
done
Then if that looks ok, add | sh to the end. So:
for file in *.[Jj][Pp][Gg] ;do
echo mv -vi \"$file\" `jhead $file|
grep Date|
cut -b 16-|
sed -e 's/:/-/g' -e 's/ /_/g' -e 's/$/.jpg/g'` ;
done | sh
for i in *; do mv $i $(echo $i|sed 's/AAA/BBB/'); done
The parentheses capture particular strings for use by the backslashed numbers.
ls F00001-0708-*|sed 's|^F0000\(.*\)|mv & F000\1|' | bash
Some examples that work for me:
$ tree -L 1 -F .
.
├── A.Show.2020.1400MB.txt
└── Some Show S01E01 the Loreming.txt
0 directories, 2 files
## remove "1400MB" (I: ignore case) ...
$ for f in *; do mv 2>/dev/null -v "$f" "`echo $f | sed -r 's/.[0-9]{1,}mb//I'`"; done;
renamed 'A.Show.2020.1400MB.txt' -> 'A.Show.2020.txt'
## change "S01E01 the" to "S01E01 The"
## \U& : change (here: regex-selected) text to uppercase;
## note also: no need here for `\1` in that regex expression
$ for f in *; do mv 2>/dev/null "$f" "`echo $f | sed -r "s/([0-9] [a-z])/\U&/"`"; done
$ tree -L 1 -F .
.
├── A.Show.2020.txt
└── Some Show S01E01 The Loreming.txt
0 directories, 2 files
$
2>/dev/null suppresses extraneous output (warnings ...)
reference [this thread]: https://stackoverflow.com/a/2372808/1904943
change case: https://www.networkworld.com/article/3529409/converting-between-uppercase-and-lowercase-on-the-linux-command-line.html