I am using
ls -ltr /homedir/mydirectory/work/ |tail -n 1|cut -d ' ' -f 10
But this is a very crude way of getting the desired result.And also its unreliable.
The output I get on simply executing
ls -ltr /homedir/mydirectory/work/ |tail -n 1
is
-rw-r--r-- 1 user pusers 1764 Apr 1 12:06 firstfile.xml
So here I get the file name.
But if the output on doing the above command is like
-rw-r--r-- 100 user pusers 1764 Apr 1 12:06 firstfile.xml
the first command fails ! And understandably as I am cutting the result from the 10th character which does not hold valid now.
So how to refine it.
Why do you use the -l flag for ls if you don't need it? Make ls simply output the filenames if you don't need more information instead of trying to "parse" its non-unified output (raping poor text processing utilities...).
LAST_MODIFIED_FILE=`ls -tr | tail -n 1`
If you really want to achieve this using your method, then, use awk instead of cut
ls -ltr /var/log/ |tail -n 1| awk '{print $9}'
Extended user user529758 answer which can give result as per file name
use below commnad as per the file name
ls -tr Filename* | tail -n 1
Related
I need to display the filesize and the filename. Like this:
4.0K Desktop
I'm extracting these two fields using cut from the ls -l output:
ls -lhS | cut -d' ' -f5,9
Due to multiple spaces in the ls -l output, I'm getting a few erroneous outputs, like:
4.0K 19:54
4.0K 19:55
6
18:39
31
25
How should I fix this?
I need to accomplish this task using pipes only and no bash scripting ( output could be multiple pipes ) and preferably no sed, awk.
If no alternative to sed or awk is available- use of sed is OK.
You can avoid parsing ls output and use the stat command which comes as part of GNU coreutils in bash for detailed file information.
# -c --format=FORMAT
# use the specified FORMAT instead of the default; output a newline after each use of FORMAT
# %n File name
# %s Total size, in bytes
stat -c '%s %n' *
You can use translate character command before using cut.
ls -lhS | tr -s ' ' | cut -d' ' -f 5,9
Or you could just submit to awk:
$ ls -lhS | awk '$0=$5 OFS $9'
ie. replace whole record $0 with fields $5 and $9 separated by output field separator OFS.
I have a bunch of log files in a folder. When I cd into the folder and look at the files it looks something like this.
$ ls -lhat
-rw-r--r-- 1 root root 5.3K Sep 10 12:22 some_log_c48b72e8.log
-rw-r--r-- 1 root root 5.1M Sep 10 02:51 some_log_cebb6a28.log
-rw-r--r-- 1 root root 1.1K Aug 25 14:21 some_log_edc96130.log
-rw-r--r-- 1 root root 406K Aug 25 14:18 some_log_595c9c50.log
-rw-r--r-- 1 root root 65K Aug 24 16:00 some_log_36d179b3.log
-rw-r--r-- 1 root root 87K Aug 24 13:48 some_log_b29eb255.log
-rw-r--r-- 1 root root 13M Aug 22 11:55 some_log_eae54d84.log
-rw-r--r-- 1 root root 1.8M Aug 12 12:21 some_log_1aef4137.log
I want to look at the most recent messages in the most recent log file. I can now manually copy the name of the most recent log and then perform a tail on it and that will work.
$ tail -n 100 some_log_c48b72e8.log
This does involve manual labor so instead I would like to use bash-fu to do this.
I currently found this way to do it;
filename="$(ls -lat | sed -n 2p | tail -c 30)"; tail -n 100 $filename
It works, but I am bummed out that I need to save data into a variable to do it. Is it possible to do this in bash without saving intermediate results into a variable?
tail -n 100 "$(ls -at | head -n 1)"
You do not need ls to actually print timestamps, you just need to sort by them (ls -t). I added the -a option because it was in your original code, but note that this is not necessary unless your logfiles are "dot files", i.e. starting with a . (which they shouldn't).
Using ls this way saves you from parsing the output with sed and tail -c. (And you should not try to parse the output of ls.) Just pick the first file in the list (head -n 1), which is the newest. Putting it in quotation marks should save you from the more common "problems" like spaces in the filename. (If you have newlines or similar in your filenames, fix your filenames. :-D )
Instead of saving into a variable, you can use command substitution in-place.
A truly ls-free solution:
tail -n 100 < <(
for f in *; do
[[ $f -nt $newest ]] && newest=$f
done
cat "$newest"
)
There's no need to initialize newest, since any file will be newer than the null file named by the empty string.
It's a bit verbose, but it's guaranteed to work with any legal file name. Save it to a shell function for easier use:
tail_latest () {
dir=${1:-.}
size=${2:-100}
for f in "$dir"/*; do
[[ $f -nt $newest ]] && newest=$f
done
tail -f "$size" "$newest"
}
Some examples:
# Default of 100 lines from newest file in the current directory
tail_latest
# 200 lines from the newest file in another directory
tail_latest /some/log/dir 200
A plug for zsh: glob qualifiers let you sort the results of a glob directly, making it much easier to get the newest file.
tail -n 100 *(om[1,1])
om sorts the results by modification time (newest first). [1,1] limits the range of files matched to the first. (I think Y1 should do the same, but it kept giving me an "unknown file attribute" error.)
Without parsing ls, you'd use stat
tail -n 100 "$(stat -c "%Y %n" * | sort -nk1,1 | tail -1 | cut -d" " -f 2-)"
Will break if your filenames contain newlines.
version 2: newlines are OK
tail -n 100 "$(
stat --printf "%Y:%n\0" * |
sort -z -t: -k1,1nr |
{ IFS=: read -d '' time filename; echo "$filename"; }
)"
You can try this way also
ls -1t | head -n 1 | xargs tail -c 50
Explanation :
ls -1rht -- list the files based on modified time in reverse order.
tail -n 1 -- get the last one file
tail -c 50 -- show the last 50 character from the file.
I need to use ls -l and I would like to have as result just the first word of the file name for instance for a result like this
-rw-r--r-- 1 root root 9 Sep 21 23:11 best file 1.txt
I would like to have only
best
as result because I need to put this value into a variable. It is ok as well if there is another way instead of using ls -l.
...sorry to bother you again...if the file is under a sub-directory, how can I hide the folder from the result? Thanks
You don't need to use ls -l (L).
Instead, use ls -1 (number one), that just outputs the names of the files, and then filter out the first column with cut:
ls -1 | cut -d' ' -f1
^
number one, not letter L
To store the value into a variable, do:
var=$(ls -1 | cut -d' ' -f1)
Note it is not a good thing to parse ls: the number of columns may vary, etc. You can read more about the topic in Why you shouldn't parse the output of ls
Update
Note there is no even need to use -1 (one), ls alone suffices:
ls | cut -d' ' -f1
As BroSlow comments below, "because they are EOL (end of line) separated across a pipe".
If you have only one row to output, this will work fine:
var=`ls -l | awk '{ print $9 }'`
echo ${var}
Or you need to use grep to filter your output for the correct file.
set -- $(ls -l)
echo ${11} # Assumes the file is the FIRST one listed.
Should do the trick. But I'm not sure if that's really what you want. For one thing, ls -l also prints an extra header line. Why do you say that you need to use ls -l? If you could state the actual problem, maybe we can find a much better solution together...
awk can pick the first word for you;
ls | awk '{print $1}'
Try:
ls -al|awk 'NR==4{ print $9 }'
Row number 4 will have first line of files. $9 indicates column 9 which will have desired word.
I'm connecting to an exadata and want to get information about "ORACLE_HOME" variable inside them. So i'm using this command:
ls -l /proc/<pid>/cwd
this is the output:
2 oracle oinstall 0 Jan 23 21:20 /proc/<pid>/cwd -> /u01/app/database/11.2.0/dbs/
i need the get the last part :
/u01/app/database/11.2.0 (i dont want the "/dbs/" there)
i will be using this command several times in different machines. So how can i get this substring from whole output?
Awk and grep are good for these types of issues.
New:
ls -l /proc/<pid>/cwd | awk '{print ($NF) }' | sed 's#/dbs/##'
Old:
ls -l /proc/<pid>/cwd | awk '{print ($NF) }' | egrep -o '^.+[.0-9]'
Awk prints the last column of the input which is your ls command and then grep grabs the beginning of that string up the last occurrence of numbers and dots. This is a situational solution and perhaps not the best.
Parsing the output of ls is generally considered sub-optimal. I would use something more like this instead:
dirname $(readlink -f /proc/<pid>/cwd)
Why does ls not work when the -l flag is passed in combination with xargs and grep?
$ ls -rt | xargs grep xyz
works, but:
$ ls -lrt | xargs grep xyz
grep: invalid option -- '-'
Usage: grep [OPTION]... PATTERN [FILE]...
Try `grep --help' for more information.
Because the output for ls -l is similar to this:
-rw-r--r-- 1 root root 1491872 2012-11-22 03:07 Xvfb_screen0
Piping this to xargs (ls -l | xargs grep xyz) is making your grep command to be
grep xyz -rw-r--r-- 1 root root 1491872 2012-11-22 03:07 Xvfb_screen0
And it does not have any sense.
edit
to answer #vladr comment here because it has better formatting than the comments box. Each whitespace separated text from the input of xargs is passed as a new param to the executed command, as you can see:
$ ls -l
total 4
-rwxrwxr-x 1 carlos carlos 18 2012-11-22 15:17 foo
$ cat foo
#!/bin/sh
echo $#
$ ls -l | xargs ./foo
10
It's possible to behave the way you say by setting the delimiter in xargs to \n:
$ ls -l | xargs -d '\n' ./foo
2
To answer your question, specifically, use ls -lrt | xargs grep xyz -- (notice the --, which signifies that any dashes - that appear afterwards are to be taken literally, not as option flags -- see #CarlosCampderrós's answer for what your command expands to), but I strongly doubt that you have the correct setup to begin with, as it is unlikely to achieve anything useful, as used.
More likely you are trying to grep for xyz in all files in reverse chronological order. If so then use ls -1rt | xargs grep xyz -- (notice dash-one -1, not dash-ell -l.) The -- is truly optional in this case (unless you expect one or more files' name(s) to begin with dash -.)