I have a set of files I want to perform an action on in a folder that i'm hoping to write a scipt for. Each file starts with mazeFilex where x can vary from any number , is there a quick and easy way to perform an action on each file? e.g. I will be doing
cat mazeFile0.txt | ./maze_ppm 5 | convert - maze0.jpg
how can I select each file knowing the file will always start with mazeFile?
for fname in mazeFile*
do
base=${fname%.txt}
base=${base#mazeFile}
./maze_ppm 5 <"$fname" | convert - "maze${base}.jpg"
done
Notes
for fname in mazeFile*; do
This codes starts the loop. Written this way, it is safe for all filenames, whether they have spaces, tabs or whatever in their names.
base=${fname%.txt}; base=${base#mazeFile}
This removes the mazeFile prefix and .txt suffix to just leave the base name that we will use for the output file.
./maze_ppm 5 <"$fname" | convert - "maze${base}.jpg"
The output filename is constructed using base. Note also that cat was unnecessary and has been removed here.
for i in mazeFile*.txt ; do ./maze_ppm 5 <$i | convert - `basename maze${i:8} .txt`.jpg ; done
You can use a for loop to run through all the filenames.
#!/bin/bash
for fn in mazeFile*; do
echo "the next file is $fn"
# do something with file $fn
done
See answer here as well: Bash foreach loop
I see you want a backreference to the number in the mazeFile. Thus I recommend John1024's answer.
Edit: removes the unnecessary ls command, per #guido 's comment.
Related
I have a folder with several files named : something_1001.txt; something_1002.txt; something_1003.txt; etc.
Inside the files there is some text. Of course each file has a different text but the structure is always the same: some lines identified with the string ">TEXT", which are the ones I am interested in.
So my goal is :
for each file in the folder, read the file's name and extract the number between "_" and ".txt"
modify all the lines in this particular file that contain the string ">TEXT" in order to make it ">{NUMBER}_TEXT"
For example : file "something_1001.txt"; change all the lines containing ">TEXT" by ">1001_TEXT"; move on to file "something_1002.txt" change all the lines containing ">TEXT" by ">1002_TEXT"; etc.
Here is the code I wrote so far :
for i in /folder/*.txt
NAME=`echo $i | grep -oP '(?<=something_/).*(?=\.txt)'`
do
sed -i -e 's/>TEXT/>${NAME}_TEXT/g' /folder/something_${NAME}.txt
done
I created a small bash script to run the code but it's not working. There seems to be syntax errors and a loop error, but I can't figure out where.
Any help would be most welcome !
There are two problems here. One is that your loop syntax is wrong; the other is that you are using single quotes around the sed script, which prevents the shell from interpolating your variable.
The grep can be avoided, anyway; the shell has good built-in facilities for extracting the base name of a file.
for i in /folder/*.txt
do
base=${i#/folder/something_}
sed -i -e "s/>TEXT/>${base%.txt}_TEXT/" "$i"
done
The shell's ${var#prefix} and ${var%suffix} variable manipulation facility produces the value of $var with the prefix and suffix trimmed off, respectively.
As an aside, avoid uppercase variable names, because those are reserved for system use, and take care to double-quote any variable whose contents may include shell metacharacters.
I am completely new to bash script. I am trying to do something really basic before using it for my actual requirement. I have written a simple code, which should print test code as many times as the number of files in the folder.
My code:
for variable in `ls test_folder`; do
echo test code
done
"test_folder" is a folder which exist in the same directory where the bash.sh file lies.
PROBLEM: If the number of files are one then, it prints single time but if the number of files are more than 1 then, it prints a different count. For example, if there are 2 files in "test_folder" then, test code gets printed 3 times.
Just use a shell pattern (aka glob):
for variable in test_folder/*; do
# ...
done
You will have to adjust your code to compensate for the fact that variable will contain something like test_folder/foo.txt instead of just foo.txt. Luckily, that's fairly easy; one approach is to start the loop body with
variable=${variable#test_folder/}
to strip the leading directory introduced by the glob.
Never loop over the output of ls! Because of word splitting files having spaces in their names will be a problem. Sure, you could set IFS to $\n, but files in UNIX can also have newlines in their names.
Use find instead:
find test_folder -maxdepth 1 -mindepth 1 -exec echo test \;
This should work:
cd "test_folder"
for variable in *; do
#your code here
done
cd ..
variable will contain only the file names
Its my first time to use BASH scripting and been looking to some tutorials but cant figure out some codes. I just want to list all the files in a folder, but i cant do it.
Heres my code so far.
#!/bin/bash
# My first script
echo "Printing files..."
FILES="/Bash/sample/*"
for f in $FILES
do
echo "this is $f"
done
and here is my output..
Printing files...
this is /Bash/sample/*
What is wrong with my code?
You misunderstood what bash means by the word "in". The statement for f in $FILES simply iterates over (space-delimited) words in the string $FILES, whose value is "/Bash/sample" (one word). You seemingly want the files that are "in" the named directory, a spatial metaphor that bash's syntax doesn't assume, so you would have to explicitly tell it to list the files.
for f in `ls $FILES` # illustrates the problem - but don't actually do this (see below)
...
might do it. This converts the output of the ls command into a string, "in" which there will be one word per file.
NB: this example is to help understand what "in" means but is not a good general solution. It will run into trouble as soon as one of the files has a space in its name—such files will contribute two or more words to the list, each of which taken alone may not be a valid filename. This highlights (a) that you should always take extra steps to program around the whitespace problem in bash and similar shells, and (b) that you should avoid spaces in your own file and directory names, because you'll come across plenty of otherwise useful third-party scripts and utilities that have not made the effort to comply with (a). Unfortunately, proper compliance can often lead to quite obfuscated syntax in bash.
I think problem in path "/Bash/sample/*".
U need change this location to absolute, for example:
/home/username/Bash/sample/*
Or use relative path, for example:
~/Bash/sample/*
On most systems this is fully equivalent for:
/home/username/Bash/sample/*
Where username is your current username, use whoami to see your current username.
Best place for learning Bash: http://www.tldp.org/LDP/abs/html/index.html
This should work:
echo "Printing files..."
FILES=(/Bash/sample/*) # create an array.
# Works with filenames containing spaces.
# String variable does not work for that case.
for f in "${FILES[#]}" # iterate over the array.
do
echo "this is $f"
done
& you should not parse ls output.
Take a list of your files)
If you want to take list of your files and see them:
ls ###Takes list###
ls -sh ###Takes list + File size###
...
If you want to send list of files to a file to read and check them later:
ls > FileName.Format ###Takes list and sends them to a file###
ls > FileName.Format ###Takes list with file size and sends them to a file###
I want to create 1000s of this one file.
All I need to replace in the file is one var
kitename = $1
But i want to do that 1000s of times to create 1000s of diff files.
I'm sure it involves a loop.
people answering people is more effective than google search!
thx
I'm not really sure what you are asking here, but the following will create 1000 files named filename.n containing 1 line each which is "kite name = n" for n = 1 to n = 1000
for i in {1..1000}
do
echo "kitename = $i" > filename.$i
done
If you have mysql installed, it comes with a lovely command line util called "replace" which replaces files in place across any number of files. Too few people know about this, given it exists on most linux boxen everywhere. Syntax is easy:
replace SEARCH_STRING REPLACEMENT -- targetfiles*
If you MUST use sed for this... that's okay too :) The syntax is similar:
sed -i.bak s/SEARCH_STRING/REPLACEMENT/g targetfile.txt
So if you're just using numbers, you'd use something like:
for a in {1..1000}
do
cp inputFile.html outputFile-$a.html
replace kitename $a -- outputFile-$a.html
done
This will produce a bunch of files "outputFile-1.html" through "outputFile-1000.html", with the word "kitename" replaced by the relevant number, inside the file.
But, if you want to read your lines from a file rather than generate them by magic, you might want something more like this (we're not using "for a in cat file" since that splits on words, and I'm assuming here you'd have maybe multi-word replacement strings that you'd want to put in:
cat kitenames.txt | while read -r a
do
cp inputFile.html "outputFile-$a.html"
replace kitename "$a" -- kitename-$a
done
This will produce a bunch of files like "outputFile-red kite.html" and "outputFile-kite with no string.html", which have the word "kitename" replaced by the relevant name, inside the file.
I am trying to iterate through files in the same directory with only one 4 in them.
Here is what I have so far. The problem with my current script is that files with any number of 4's get selected, not files with only one 4.
for i in *4*.cpp;
do
...
Sort of like [!4] but for any number of non 4 characters.
*http://www.tuxfiles.org/linuxhelp/wildcards.html
I want to iterate through file names such as me4.cpp, 4.cpp, and hi4hi.cpp
I want to ignore file names such as lala.cpp, 44.cpp, 4hi4.cpp
Thank you!
Figured it out. I tried [!4]* on a whim.
Oops turned out I didn't. That is interpreted as ([!4]) then (*)
The grep style regex you need is:
^[^4]*4[^4]*$
A bunch of not-4's after the start of the line, a 4, and another bunch of not-4's to the end of the line.
In pure shell, consider using a case statement:
for file in *4*.cpp
do
case "$file" in
(*4*4*) : Ignore;;
(*) : Process;;
esac
done
That looks for names containing 4's, and then ignores those containing 2 or more 4's.
How about using find
find ./ -regex "<regular expression>"
Assuming bash:
shopt -s extglob
for file in *([^4])4*([^4]).cpp; ...
where *([^4]) means zero or more characters that are not "4"