There's the following part in a shell script I'm writing:
(Find the latest directory in someDir which is not summary/)
latestDirName=""
for dirName in `ls -lt /user/someDir/ | head -3 | tail -n +2 | awk '{print $9}'`
do
if [ "$dirName" == "summary" ]; then
continue
fi
latestDirName=$dirName
done
Here $dirname is compared against string summary, while an echo of dirName variable during the iteration will print as summary/
This comparison part works all fine when the code is written in a file and executed.
But once this same code is put inside a function and placed in my bashrc, the comparison in if check doesn't seem to work!
Does this have anything to do with the string being a directory name, or it having the /?
What difference does it make when the same code is inside a function?
Code inside bashrc:
findLatestDir()
{
latestDirName=""
for dirName in `ls -lt /user/someDir/ | head -3 | tail -n +2 | awk '{print $9}'`
do
if [ "$dirName" == "summary" ]; then
continue
fi
latestDirName=$dirName
done
}
The scripts are called as follows:
Case #1 (code in file): $ ./findLatestDir.sh
Case #2 (function in bashrc): $ findLatestDir
Maybe you have an alias or function definition for ls in your .bashrc, which interacts poorly with your use of ls in the function? If so, explicitly saying /bin/ls in the function may solve the problem.
Parsing ls is never a good idea. Use stat instead: print out the epoch modification time, sort numerically in descending order, then find the first dir that is not "summary".
findLatestDir() (
cd /some/dir
stat -c $'%Y\t%n' */ |
sort -rn |
cut -f2 | {
while read dir; do
[[ $dir == "summary/" ]] || break
done
echo $dir
}
)
Note that the bash wildcard */ with the trailing directory limits the results to directories only.
I execute the function in a subshell so the cd command does not affect your current directory.
Related
I would like to get file (zip file) from path with this part of code file=$(cd '/path_to_zip_file' | ls -t | head -1). Instead that I got my .sh file in directory where I am running this file.
Why I can't file from /path_to_zip_file
Below is my code in .sh file
file=$(cd '/path_to_zip_file' | ls -t | head -1)
last_modified=`stat -c "%Y" $file`;
current=`date +%s`
echo $file
if [ $(($current-$last_modified)) -gt 86400 ]; then
echo 'Mail'
else
echo 'No Mail'
fi;
If you were going to use ls -t | head -1 (which you shouldn't), the cd would need to be corrected as a prior command (happening before ls takes place), not a pipeline component (running parallel with ls, with its stdout connected to ls's stdin):
set -o pipefail # otherwise, a failure of ls is ignored so long as head succeeds
file=$(cd '/path_to_zip_file' && ls -t | head -1)
A better-practice approach might look like:
newest_file() {
local result=$1; shift # first, treat our first arg as latest
while (( $# )); do # as long as we have more args...
[[ $1 -nt $result ]] && result=$1 # replace "result" if they're newer
shift # then take them off the argument list
done
[[ -e $result || -L $result ]] || return 1 # fail if no file found
printf '%s\n' "$result" # more reliable than echo
}
newest=$(newest_file /path/to/zip/file/*)
newest=${newest##*/} ## trim the path to get only the filename
printf 'Newest file is: %s\n' "$newest"
To understand the ${newest##*/} syntax, see the bash-hackers' wiki on parameter expansion.
For more on why using ls in scripts (except for output displayed to humans) is dangerous, see ParsingLs.
Bot BashFAQ #99, How do I get the latest (or oldest) file from a directory? -- and BashFAQ #3 (How can I sort or compare files based on some metadata attribute (newest / oldest modification time, size, etc)?) have useful discussion on the larger context in which this question was asked.
I am wondering why I do not get se same output from:
ls -1 -tF | head -n 1
and
echo $(ls -1 -tF | head -n 1)
I tried to get the last modified file, but using it inside a sub shell sometimes I get more than one file as result?
Why that and how to avoid?
The problem arises because you are using an unquoted subshell and -F flag for ls outputs shell special characters appended to filenames.
-F, --classify
append indicator (one of */=>#|) to entries
Executable files are appended with *.
When you run
echo $(ls -1 -tF | head -n 1)
then
$(ls -1 -tF | head -n 1)
will return a filename, and if it happens to be an executable and also be the prefix to another file, then it will return both.
For example if you have
test.sh
test.sh.backup
then it will return
test.sh*
which when echoed expands to
test.sh test.sh.backup
Quoting the subshell prevents this expansion
echo "$(ls -1 -tF | head -n 1)"
returns
test.sh*
I just found the error:
If you use echo $(ls -1 -tF | head -n 1)
the file globing mechanism may result in additional matches.
So echo "$(ls -1 -tF | head -n 1)" would avoid this.
Because if the result is an executable it contains a * at the end.
I tried to place the why -F in a comment, but now I decided to put it here:
I added the following lines to my .bashrc, to have a shortcut to get last modified files or directories listed:
function L {
myvar=$1; h=${myvar:="1"};
echo "last ${h} modified file(s):";
export L=$(ls -1 -tF|fgrep -v / |head -n ${h}| sed 's/\(\*\|=\|#\)$//g' );
ls -l $L;
}
function LD {
myvar=$1;
h=${myvar:="1"};
echo "last ${h} modified directories:";
export LD=$(ls -1 -tF|fgrep / |head -n $h | sed 's/\(\*\|=\|#\)$//g'); ls -ld $LD;
}
alias ol='L; xdg-open $L'
alias cdl='LD; cd $LD'
So now I can use L (or L 5) to list the last (last 5) modified files. But not directories.
And with L; jmacs $L I can open my editor, to edit it. Traditionally I used my alias lt='ls -lrt' but than I have to retype the name...
Now after mkdir ... I use cdl to change to that dir.
for d in */ ; do
cd $d
NUM = $(echo ${PWD##*/} | grep -q "*abc*");
if [[ "$NUM" -ne "0" ]]; then
pwd
fi
cd ..
done
Here I'm trying to match a folder name to some substring 'abc' in the name of the folder and check if the output of the grep is not 0. But it gives me an error which reads that NUM: command not found
An error was addressed in comments.
NUM = $(echo ${PWD##*/} | grep -q "*abc*"); should be NUM=$(echo ${PWD##*/} | grep -q "*abc*");.
To clarify, the core problem would be to be able to match current directory name to a pattern.
You can probably simply the code to just
if grep -q "*abc*" <<< "${PWD##*/}" 2>/dev/null; then
echo "$PWD"
# Your rest of the code goes here
fi
You can use the exit code of the grep directly in a if-conditional without using a temporary variable here ($NUM here). The condition will pass if grep was able to find a match. The here-string <<<, will pass the input to grep similar to echo with a pipeline. The part 2>/dev/null is to just suppress any errors (stderr - file descriptor 2) if grep throws!
As an additional requirement asked by OP, to negate the conditional check just do
if ! grep -q "*abc*" <<< "${PWD##*/}" 2>/dev/null; then
I need to make a for loop that loops for every item in a directory.
My issue is the for loop is not acting as I would expect it to.
cd $1
local leader=$2
if [[ $dOpt = 0 ]]
then
local items=$(ls)
local nitems=$(ls |grep -c ^)
else
local items=$(ls -l | egrep '^d' | awk '{print $9}')
local nitems=$(ls -l | egrep '^d' | grep -c ^)
fi
for item in $items;
do
printf "${CYAN}$nitems\n${NONE}"
let nitems--
if [[ $nitems -lt 0 ]]
then
exit 4
fi
printf "${YELLOW}$item\n${NONE}"
done
dOpt is just a switch for a script option.
The issue I'm having is the nitems count doesn't decrease at all, it's as if the for loop is only going in once. Is there something I'm missing?
Thanks
Goodness gracious, don't rely on ls to iterate over files.
local is only useful in functions.
Use filename expansion patterns to store the filenames in an array.
cd "$1"
leader=$2 # where do you use this?
if [[ $dOpt = 0 ]]
then
items=( * )
else
items=( */ ) # the trailing slash limits the results to directories
fi
nitems=${#items[#]}
for item in "${items[#]}" # ensure the quotes are present here
do
printf "${CYAN}$((nitems--))\n${NONE}"
printf "${YELLOW}$item\n${NONE}"
done
Using this technique will safely handle files with spaces, even newlines, in the name.
Try this:
if [ "$dOpt" == "0" ]; then
list=(`ls`)
else
list=(`ls -l | egrep '^d' | awk '{print $9}'`)
fi
for item in `echo $list`; do
... # do something with item
done
Thanks for all the suggestions. I found out the problem was changing $IFS to ":". While I meant for this to avoid problems with whitespaces in the filename, it just complicated things.
I need a command that will return the top level base directory for a specified path in bash.
I have an approach that works, but seems ugly:
echo "/go/src/github.myco.com/viper-ace/psn-router" | cut -d "/" -f 2 | xargs printf "/%s"
It seems there is a better way, however all the alternatives I've seen seem worse.
Thanks for any suggestions!
One option is using awk:
echo "/go/src/github.myco.com/viper-ace/psn-router" |
awk -F/ '{print FS $2}'
/go
As a native-bash approach forking no subshells and invoking no other programs (thus, written to minimize overhead), which works correctly in corner cases including directories with newlines:
topdir() {
local re='^(/+[^/]+)'
[[ $1 =~ $re ]] && printf '%s\n' "${BASH_REMATCH[1]}"
}
Like most other solutions here, invocation will then look something like outvar=$(topdir "$path").
To minimize overhead even further, you could pass in the destination variable name rather than capturing stdout:
topdir() {
local re='^(/+[^/]+)'
[[ $1 =~ $re ]] && printf -v "$2" '%s' "${BASH_REMATCH[1]}"
}
...used as: topdir "$path" outvar, after which "$outvar" will expand to the result.
not sure better but with sed
$ echo "/go/src/github.myco.com/viper-ace/psn-router" | sed -E 's_(/[^/]+).*_\1_'
/go
Here's a sed possibility. Still ugly. Handles things like ////////home/path/to/dir. Still blows up on newlines.
$ echo "////home/path/to/dir" | sed 's!/*\([^/]*\).*!\1!g'
/home
Newlines breaking it:
$ cd 'testing '$'\n''this'
$ pwd
/home/path/testing
this
$ pwd | sed 's!/*\([^/]*\).*!/\1!g'
/home
/this
If you know your directories will be rather normally named, your and anubhava's solutions certainly seem to be more readable.
This is bash, sed and tr in a function :
#!/bin/bash
function topdir(){
dir=$( echo "$1" | tr '\n' '_' )
echo "$dir" | sed -e 's#^\(/[^/]*\)\(.*\)$#\1#g'
}
topdir '/go/src/github.com/somedude/someapp'
topdir '/home/somedude'
topdir '/with spaces/more here/app.js'
topdir '/with newline'$'\n''before/somedir/somefile.txt'
Regards!