I'm not an expert in bash coding and I'm trying to do one interative-like code to help me in my work.
I have a file that contains some numbers (coordinates), and I'm trying to make a code to read some specific numbers from the file and then store them in an array. Modify that array using some arithmetic operation and then replace the numbers in the original file with the modified array. So far I've done everything except replacing the numbers in the file, I tried using sed but it does not change the file. The original numbers are stored in an array called "readfile" and the new numbers are stored in an array called "d".
I'm trying to use sed in this way: sed -i 's/${readfile[$j]}/${d[$k]}/' file.txt
And I loop j and k to cover all the numbers in the arrays. Everything seems to work but the file is not being modified. After some digging, I'm noticing that sed is not reading the value of the array, but I do not know how to fix that.
Your help is really appreciated.
When a file isn't modified by sed -i, it means sed didn't find any matches to modify. Your pattern is wrong somehow.
After using " instead of ' so that the variables can actually be evaluated inside the string, look at the contents of the readfile array and check whether it actually matches the text. If it seems to match, look for special characters in the pattern, characters that would mean something specific to sed (the most common mistake is /, which will interfere with the search command).
The fix for special characters is either to (1) escape them, e.g. \/ instead of just /, or (2) (and especially for /) to use another delimiter for the search/replace command (instead of s/foo/bar/ you can use s|foo|bar| or s,foo,bar, etc - pretty much any delimiter works, so you can pick one that you know isn't in the pattern string).
If you post data samples and more of your script, we can look at where you went wrong.
Related
Command ffmpeg -i file-1.mp4 -vf ass=file-1a.ass burned-1.mp4
works to burn file-1a.ass subtitles on file-1.mp4 video.
But each time I have to reiterate the same command on over 40 different videos and subtitles and each time I have to wait for rendering the output.
So perhaps there is a way to automatically reiterate the same command on all the files.
Looking for a reply found the loop command
for f in *; do ffmpeg $f;
But I am confused how to use it with 2 files, the .mp4 and the .ass file, and also the output file which should have the same number
I imagine should put the same name on each couple of files, such as:
1.mp4 1.ass
2.mp4 2.ass
3.mp4 3.ass
etc
and then
for f in *; do ffmpeg -i $f.mp4 -vf ass=$f.ass $f-output.mp4
But I have no clear idea
You have the right idea. But it won’t work if the loop executes with f == 1.mp4, then again with f == 1.ass, and so on.
So you want to modify the loop to only iterate over .mp4 files. Then you want to strip the .mp4 extension from the value of f, that is, strip the last 4 characters from the value of f, using ${f:0: -4} (this means “get a substring of f, starting at character 0 and ending at 5 characters before the end”).
You obviously want to terminate the loop with done. I also suggest wrapping the parameters in quotes, to prevent word splitting (that is, if the filenames contain certain characters, they might be split into multiple arguments to ffmpeg).
Putting it all together:
for f in *.mp4; do f=${f%.*}; ffmpeg -i "$f.mp4" -vf ass="$f.ass" "$f-output.mp4"; done
Of course, once you have run this, you need to get rid of all the output files before you can run it again. Or you can just put the output files in a different directory to begin with.
Edit: Another user posted an answer, which seems to have been deleted. It was a good answer but lacked explanation. It was basically the same as my answer, except that it used ${f%.mp4} to strip the .mp4 extension. My answer is probably slightly more complex but slightly more efficient, so it’s basically a matter of personal preference.
Edit 2: Based on the link provided by llogan’s comment, I have made these changes:
Remove the quotes in the assignment, as assignments are not subject to word splitting (this is also stated in the bash man page).
Use ${f%.*} to strip the extension. This strips a dot followed by any sequence of characters from the end. It looks for the shortest possible match, so it’s really looking for a dot followed by any sequence of non-dot characters at the end.
I'm trying to create a for-loop to go through all the items from an array, and add the items to a string. The tags are given as a single string with format "tag1 tag2 tag3", and the tagging parameter can be given as many times as I want with the single command with syntax "-tag tag1 -tag -tag2 -tag tag3". I'm unable to create a for loop for the job, and I'm a little confused what is wrong with my code.
TAGS="asd fgh jkl zxc bnm" # Amount of tags varies, but there is always at least one
ARRAY=($TAGS)
TAGSTOBEADDED=""
for i in "$ARRAY[#]"
do
STRINGTOBEADDED="-tag ${ARRAY[$i]}"
$TAGSTOBEADDED=$TAGSTOBEADDED+$STRINGTOBEADDED
done
command $TAGSTOBEADDED
First, your array sintax is wrong as #oguz ismail said. To iter through array items you shold use this:
for i in "${ARRAY[#]}"; { echo $i;}
Second $TAGSTOBEADDED=$TAGSTOBEADDED+$STRINGTOBEADDED this is also fail.
Variables are set like so var="$var 123" you don't need $ in front of var name if you want to change it. Back to code. In this example you dont even need an array, just use TAGS var(without ""):
for i in $TAGS; { TAGSTOBEADDED+="-tag $i"; }
First: avoid storing lists of things in space-delimited strings (as you're currently doing with TAGS and TAGSTOBEADDED) -- there are a bunch of things that can go wrong if they have any "funny" characters (or if IFS gets changed). Use an array instead. Storing them as a string and then converting doesn't help; all of the same potential problems apply during the conversion.
I also recommend using lower- or mixed-case variable names in scripts, since there are a bunch of all-caps names with special meanings, and accidentally using one of those for something else can have weird effects. So, to define the array of tags, I'd just use this:
tags=(asd fgh jkl zxc bnm)
You also have a number of syntax errors in the script. In this line:
for i in "$ARRAY[#]"
... the shell will try to expand $ARRAY as a plain variable (not an array), and then treat "[#]" as just some unrelated characters that go after it. You need braces around the variable refence (like "${ARRAY[#]}") any time you're doing anything nontrivial with a variable reference. BTW, this idiom -- including double-quotes, braces, square-brackets and at-sign -- is what you almost always want when getting the contents of an array.
In this line:
STRINGTOBEADDED="-tag ${ARRAY[$i]}"
$i will expand to one of the array elements, not its index. That is, it'll expand to something like:
STRINGTOBEADDED="-tag ${ARRAY[asd]}"
...which doesn't make any sense. You just want
STRINGTOBEADDED="-tag $i"
...except you don't want that either, because (as I said before) storing lists of things space-delimited in a string is a bad idea. But I'll get to that because fixing it will involve the next line:
$TAGSTOBEADDED=$TAGSTOBEADDED+$STRINGTOBEADDED
There are two problems here: you don't want a dollar sign on the variable being assigned to ($varname gets the value of a variable; anytime you're setting it, don't use the $). Also the + isn't needed to add strings, you just stick them end to end. Well, you'd need to add a space in between, something like one of these:
TAGSTOBEADDED=$TAGSTOBEADDED" "$STRINGTOBEADDED
TAGSTOBEADDED="$TAGSTOBEADDED $STRINGTOBEADDED"
(Generally, you should have double-quotes around all variable references; on the right side of a plain assignment is one of the few places it's safe to leave them unquoted, but I tend to prefer to just double-quote always rather than try to remember all of the exceptions about where it's safe and where it isn't. Plus, quoting just the space looks weird.)
But you don't want to do that either, because (again) space-delimited strings are a bad way to do things. Use an array. So before the loop, create an empty array instead of an empty string:
tagstobeadded=()
...and then inside the loop, append to it with +=( ):
tagstobeadded+=(-tag "$i")
...and then at the end, use it with all the appropriate quotes, braces, etc:
command "${tagstobeadded[#]}"
So, with all of these changes, here's what I'd recommend:
tags=(asd fgh jkl zxc bnm)
tagstobeadded=()
for i in "${tags[#]}"
do
tagstobeadded+=(-tag "$i")
done
command "${tagstobeadded[#]}"
I am trying to read below CSV file content line by line in Perl.
CSV File Content:
A7777777.A777777777.XXX3604,XXX,3604,YES,9
B9694396.B216905785.YYY0018,YYY,0018,YES,13
C9694396.C216905785.ZZZ0028,ZZZ,0028,YES,16
I am able to split line content using below code and able to verify the content too:
#column_fields1 = split(',', $_);
print $column_fields1[0],"\n";
I am also trying to find the second part on the first column of CSV file (i.e., A777777777 or B216905785 or C216905785) – the first column delimited with . using the below code and I am unable to get it.
Instead, just a new line printed.
my ($v1, $v2, $v3) = split(".", $column_fields1[0]);
print $v2,"\n";
Can someone suggest me how to split the array element and get the above value?
On my functionality, I need the first column value altogether at someplace and just only the second part at someplace.
Below is my code:
use strict;
use warnings;
my $dailybillable_tab_section1_file = "./sql/demanding_01_T.csv";
open(FILE, $dailybillable_tab_section1_file) or die "Could not read from $dailybillable_tab_section1_file, program halting.";
my #column_fields1;
my #column_fields2;
while (<FILE>)
{
chomp;
#column_fields1 = split(',', $_);
print $column_fields1[0],"\n";
my ($v1, $v2, $v3) = split(".",$column_fields1[0]);
print $v2,"\n";
if($v2 ne 'A777777777')
{
…
…
…
}
else
{
…
…
…
}
}
close FILE;
split takes a regex as its first argument. You can pass it a string (as in your code), but the contents of the string will simply be interpreted as a regex at runtime.
That's not a problem for , (which has no special meaning in a regex), but it breaks with . (which matches any (non-newline) character in a regex).
Your attempt to fix the problem with split "\." fails because "\." is identical to ".": The backslash has its normal string escape meaning, but since . isn't special in strings, escaping it has no effect. You can see this by just printing the resulting string:
print "\.\n"; # outputs '.', same as print ".\n";
That . is then interpreted as a regex, causing the problems you have observed.
The normal fix is to just pass a regex to split:
split /\./, $string
Now the backslash is interpreted as part of the regex, forcing . to match itself literally.
If you really wanted to pass a string to split (I'm not sure why you'd want to do that), you could also do it like this:
split "\\.", $string
The first backslash escapes the second backslash, giving a two character string (\.), which when interpreted as a regex means the same thing as /\./.
If you look at the documentation for split(), you'll see it gives the following ways to call the function:
split /PATTERN/,EXPR,LIMIT
split /PATTERN/,EXPR
split /PATTERN/
split
In three of those examples, the first argument to the function is /PATTERN/. That is, split() expects to be given a regular expression which defines how the input string is split apart.
It's very important to realise that this argument is a regex, not a string. Unfortunately, Perl's parser doesn't insist on that. It allows you to use a first argument which looks like a string (as you have done). But no matter how it looks, it's not a string. It's a regex.
So you have confused yourself by using code like this:
split(".",$COLUMN_FIELDS1[0])
If you had made the first argument look like a regex, then you would be more likely to realise that the first argument is a regex and that, therefore, a dot needs to be escaped to prevent it being interpreted as a metacharacter.
split(/\./, $COLUMN_FIELDS1[0])
Update: It's generally accepted among Perl programmers, that variable with upper case names are constants and don't change their values. By using upper case names for standard variables, you are likely to confuse the next person who edits your code (who could well be you in six months time).
I'm trying to get an array containing the full current directory path in zsh. I'm currently using
local pwd="${PWD/#$HOME/~}"
pwd_list=(${(s:/:)pwd})
Which works except for one problem, it treats the starting / as a directory split too. I'd like my array to be like
/
usr
lib
php
instead of
usr
lib
php
I can see 2 ways of doing this but I'm unaware of how to do either in zsh. The first idea is to simple do a push and force a new element to the beginning (after the split).
The second, would be to alter the split to ignore the first / when parsing.
How can I resolve this to get an accurate directory path with minimal overhead into an array?
do you really need the first /? Assuming you're using a script to use the results of that, can't you just cd / to just start from there?
Anyways... is this what you want?
local pwd="${PWD/#$HOME/~}"
pwd_list=(${(s:/:)pwd})
pwd_list=('/' $pwd_list)
I think you're thinking about it slightly wrong. If you split "/usr/lib/php" on "/", you should get four elements, the first of which is an empty string. If you join those array elements back together with "/", you get the original path. Trying to think of the first element of "/" means you're treating the splitting inconsistently, which will make everything else harder.
So the problem really is that you're only getting three elements instead of four: the empty first element is getting dropped. You can fix that by quoting, like this:
local pwd="${PWD/#$HOME/~}"
pwd_list=( "${(s:/:)pwd}" )
(The extra space next to the outer parentheses isn't necessary, but it makes it a little easier to read.) You can even combine that into one expression:
pwd_list=( "${(s:/:)${PWD/#$HOME/~}}" )
I need to find out if a file or directory name contains any extension in Unix for a Bourne shell scripting.
The logic will be:
If there is a file extension
Remove the extension
And use the file name without the extension
This is my first question in SO so will be great to hear from someone.
The concept of an extension isn't as strictly well-defined as in traditional / toy DOS 8+3 filenames. If you want to find file names containing a dot where the dot is not the first character, try this.
case $filename in
[!.]*.*) filename=${filename%.*};;
esac
This will trim the extension (as per the above definition, starting from the last dot if there are several) from $filename if there is one, otherwise no nothing.
If you will not be processing files whose names might start with a dot, the case is superfluous, as the assignment will also not touch the value if there isn't a dot; but with this belt-and-suspenders example, you can easily pick the approach you prefer, in case you need to extend it, one way or another.
To also handle files where there is a dot, as long as it's not the first character (but it's okay if the first character is also a dot), try the pattern ?*.*.
The case expression in pattern ) commands ;; esac syntax may look weird or scary, but it's quite versatile, and well worth learning.
I would use a shell agnostic solution. Runing the name through:
cut -d . -f 1
will give you everything up to the first dot ('-d .' sets the delimeter and '-f 1' selects the first field). You can play with the params (try '--complement' to reverse selection) and get pretty much anything you want.