I have a fairly large list of websites in "file.txt" and wanted to check if the words "Hello World!" in the site in the list using looping and curl.
i.e in "file.txt" :
blabla.com
blabla2.com
blabla3.com
then my code :
#!/bin/bash
put() {
printf "list : "
read list
run=$(cat $list)
}
put
scan_list() {
for run in $(cat $list);do
if [[ $(curl -skL ${run}) =~ "Hello World!" ]];then
printf "${run} Hello World! \n"
else
printf "${run} No Hello:( \n"
fi
done
}
scan_list
this takes a lot of time, is there a way to make the checking process faster?
Use xargs:
% tr '\12' '\0' < file.txt | \
xargs -0 -r -n 1 -t -P 3 sh -c '
if curl -skL "$1" | grep -q "Hello World!"; then
echo "$1 Hello World!"
exit
fi
echo "$1 No Hello:("
' _
Use tr to convert returns in the file.txt to nulls (\0).
Pass through xargs with -0 option to parse by nulls.
The -r option prevents the command from being ran if the input is empty. This is only available on Linux, so for macOS or *BSD you will need to check that file.txt is not empty before running.
The -n 1 permits only one file per execution.
The -t option is debugging, it prints the command before it is ran.
We allow 3 simultaneous commands in parallel with the -P 3 option.
Using sh -c with a single quoted multi-line command, we substitute $1 for the entries from the file.
The _ fills in the $0 argument, so our entries are $1.
Related
I have made two programms and I'm trying to call the one from the other but this is appearing on my screen:
cp: cannot stat ‘PerShip/.csv’: No such file or directory
cp: target ‘tmpship.csv’ is not a directory
I don't know what to do. Here are the programms. Could somebody help me please?
#!/bin/bash
shipname=$1
imo=$(grep "$shipname" shipsNAME-IMO.txt | cut -d "," -f 2)
cp PerShip/$imo'.csv' tmpship.csv
dist=$(octave -q ShipDistance.m 2>/dev/null)
grep "$shipname" shipsNAME-IMO.txt | cut -d "," -f 2 > IMO.txt
idnumber=$(cut -b 4-10 IMO.txt)
echo $idnumber,$dist
#!/bin/bash
rm -f shipsdist.csv
for ship in $(cat shipsNAME-IMO.txt | cut -d "," -f 1)
do
./FindShipDistance "$ship" >> shipsdist.csv
done
cat shipsdist.csv | sort | head -n 1
The code and error messages presented suggest that the second script is calling the first with an empty command-line argument. That would certainly happen if input file shipsNAME-IMO.txt contained any empty lines or otherwise any lines with an empty first field. An empty line at the beginning or end would do it.
I suggest
using the read command to read the data, and manipulating IFS to parse out comma-delimited fields
validating your inputs and other data early and often
making your scripts behave more pleasantly in the event of predictable failures
More generally, using internal Bash features instead of external programs where the former are reasonably natural.
For example:
#!/bin/bash
# Validate one command-line argument
[[ -n "$1" ]] || { echo empty ship name 1>&2; exit 1; }
# Read and validate an IMO corresponding to the argument
IFS=, read -r dummy imo tail < <(grep -F -- "$1" shipsNAME-IMO.txt)
[[ -f PerShip/"${imo}.csv" ]] || { echo no data for "'$imo'" 1>&2; exit 1; }
# Perform the distance calculation and output the result
cp PerShip/"${imo}.csv" tmpship.csv
dist=$(octave -q ShipDistance.m 2>/dev/null) ||
{ echo "failed to compute ship distance for '${imo}'" 2>&1; exit 1; }
echo "${imo:3:7},${dist}"
and
#!/bin/bash
# Note: the original shipsdist.csv will be clobbered
while IFS=, read -r ship tail; do
# Ignore any empty ship name, however it might arise
[[ -n "$ship" ]] && ./FindShipDistance "$ship"
done < shipsNAME-IMO.txt |
tee shipsdist.csv |
sort |
head -n 1
Note that making the while loop in the second script part of a pipeline will cause it to run in a subshell. That is sometimes a gotcha, but it won't cause any problem in this case.
At fisrt,I have write the code,and it run well.
# version1
all_num=10
thread_num=5
a=$(date +%H%M%S)
seq 1 ${all_num} | xargs -n 1 -I {} -P ${thread_num} sh -c 'echo abc{}'
b=$(date +%H%M%S)
echo -e "startTime:\t$a"
echo -e "endTime:\t$b"
Now I want to extract code into a funciton,but it was wrong,how to fix it?
get_file(i){
echo "abc"+i
}
all_num=10
thread_num=5
a=$(date +%H%M%S)
seq 1 ${all_num} | xargs -n 1 -I {} -P ${thread_num} sh -c "$(get_file {})"
b=$(date +%H%M%S)
echo -e "startTime:\t$a"
echo -e "endTime:\t$b"
Because /bin/sh isn't guaranteed to have support for either printing text that when evaluates defines your function, or exporting functions through the environment, we need to do this the hard way, just duplicating the text of the function inside the copy of sh started by xargs.
Other questions already exist in this site describing how to accomplish this with bash, which is quite considerably easier. See f/e How can I use xargs to run a function in a command substitution for each match?
#!/bin/sh
all_num=10
thread_num=5
batch_size=1 # but with a larger all_num, turn this up to start fewer copies of sh
a=$(date +%H%M%S) # warning: this is really inefficient
seq 1 ${all_num} | xargs -n "${batch_size}" -P "${thread_num}" sh -c '
get_file() { i=$1; echo "abc ${i}"; }
for arg do
get_file "$arg"
done
' _
b=$(date +%H%M%S)
printf 'startTime:\t%s\n' "$a"
printf 'endTime:\t%s\n' "$b"
Note:
echo -e is not guaranteed to work with /bin/sh. Moreover, for a shell to be truly compliant, echo -e is required to write -e to its output. See Why is printf better than echo? on UNIX & Linux Stack Exchange, and the APPLICATION USAGE section of the POSIX echo specification.
Putting {} in a sh -c '...{}...' position is a Really Bad Idea. Consider the case where you're passed in a filename that contains $(rm -rf ~)'$(rm -rf ~)' -- it can't be safely inserted in an unquoted context, or a double-quoted context, or a single-quoted context, or a heredoc.
Note that seq is also nonstandard and not guaranteed to be present on all POSIX-compliant systems. i=0; while [ "$i" -lt "$all_num" ]; do echo "$i"; i=$((i + 1)); done is an alternative that will work on all POSIX systems.
I would like to run commands such as "history" or "!23" off of a pipe.
How might I achieve this?
Why does the following command not work?
echo "history" | xargs eval $1
To answer (2) first:
history and eval are both bash builtins. So xargs cannot run either of them.
xargs does not use $1 arguments. man xargs for the correct syntax.
For (1), it doesn't really make much sense to do what you are attempting because shell history is not likely to be synchronised between invocations, but you could try something like:
{ echo 'history'; echo '!23'; } | bash -i
or:
{ echo 'history'; echo '!23'; } | while read -r cmd; do eval "$cmd"; done
Note that pipelines run inside subshells. Environment changes are not retained:
x=1; echo "x=2" | while read -r cmd; do eval "$cmd"; done; echo "$x"
You can try like this
First redirect the history commands to a file (cut out the line numbers)
history | cut -c 8- > cmd.txt
Now Create this script hcmd.sh(Referred to this Read a file line by line assigning the value to a variable)
#!/bin/bash
while IFS='' read -r line || [[ -n "$line" ]]; do
echo "Text read from file: $line"
$line
done < "cmd.txt"
Run it like this
./hcmd.sh
I tried the following:
#!/bin/bash
while read device; do
name=$(echo "$device" | awk '{ print $1 }')
ip=$(echo "$device" | awk '{ print $2 }')
while read creds; do
community=$(echo "$creds" | awk '{ print $1 }')
version=$(echo "$creds" | awk '{ print $2 }')
mkdir -p walks/$name;
`echo -e "snmpwalk -v$version -c \x27$community\x27 $ip system > walks/$name/$community-$version.txt
done < <(##MySQL query that returns tuples in form: (snmp_ro,(1,2c,3))##")
done < <(cat devices.txt)
exit 0
This is meant to go through and find the snmp string and version of each device.
devices.txt is a list of devices in form: hostname ip
It doesn't create the file: walks/$name/$community-$version.txt, and it only seems to run through the walks 1 at a time, something I don't want.
Use & to put the contents you want backgrounded in, well, the background.
pids=( )
while read -r -u 3 name ip _; do
while read -r -u 4 community version _; do
mkdir -p "walks/$name"
snmpwalk -v"$version" -c "$community" "$ip" system \
</dev/null >"walks/$name/$community-$version.txt" & pids+=( "$!" )
done 4< <(: get data for "$name" and "$ip")
done 3<devices.txt
wait "${pids[#]}"
Other items of note:
read can already split fields into their own variables; using awk for this is silly.
The _ in read -r foo bar _ ensures that if more than two columns exist in the input file, the third column and onward are discarded (actually, put into a variable named _, but this is considered discard by convention) rather than appended to bar.
Make a habit of quoting expansions unless you have a specific and compelling reason to do otherwise; otherwise, you get string-splitting and glob expansion of string contents.
This example puts each input stream on its own file descriptor, and redirects each read to its own FD. This prevents any other content within your loop from consuming stdin.
I've written the bash script (searchuser) which should display all the users who are executing a specific program or a script (at least a bash script). But when searching for scripts fails because the command the SO is executing is something like bash scriptname.
This script acts parsing the ps command output, it search for all the occurrences of the specified program name, extracts the user and the program name, verifies if the program name is that we're searching for and if it's it displays the relevant information (in this case the user name and the program name, might be better to output also the PID, but that is quite simple). The verification is accomplished to reject all lines containing program names which contain the name of the program but they're not the program we are searching for; if we're searching gedit we don't desire to find sgedit or gedits.
Other issues I've are:
I would like to avoid the use of a tmp file.
I would like to be not tied to GNU extensions.
The script has to be executed as:
root# searchuser programname <invio>
The script searchuser is the following:
#!/bin/bash
i=0
search=$1
tmp=`mktemp`
ps -aux | tr -s ' ' | grep "$search" > $tmp
while read fileline
do
user=`echo "$fileline" | cut -f1 -d' '`
prg=`echo "$fileline" | cut -f11 -d' '`
prg=`basename "$prg"`
if [ "$prg" = "$search" ]; then
echo "$user - $prg"
i=`expr $i + 1`
fi
done < $tmp
if [ $i = 0 ]; then
echo "No users are executing $search"
fi
rm $tmp
exit $i
Have you suggestion about to solve these issues?
One approach might looks like such:
IFS=$'\n' read -r -d '' -a pids < <(pgrep -x -- "$1"; printf '\0')
if (( ! ${#pids[#]} )); then
echo "No users are executing $1"
fi
for pid in "${pids[#]}"; do
# build a more accurate command line than the one ps emits
args=( )
while IFS= read -r -d '' arg; do
args+=( "$arg" )
done </proc/"$pid"/cmdline
(( ${#args[#]} )) || continue # exited while we were running
printf -v cmdline_str '%q ' "${args[#]}"
user=$(stat --format=%U /proc/"$pid") || continue # exited while we were running
printf '%q - %s\n' "$user" "${cmdline_str% }"
done
Unlike the output from ps, which doesn't distinguish between ./command "some argument" and ./command "some" "argument", this will emit output which correctly shows the arguments run by each user, with quoting which will re-run the given command correctly.
What about:
ps -e -o user,comm | egrep "^[^ ]+ +$1$" | cut -d' ' -f1 | sort -u
* Addendum *
This statement:
ps -e -o user,pid,comm | egrep "^\s*\S+\s+\S+\s*$1$" | while read a b; do echo $a; done | sort | uniq -c
or this one:
ps -e -o user,pid,comm | egrep "^\s*\S+\s+\S+\s*sleep$" | xargs -L1 echo | cut -d ' ' -f1 | sort | uniq -c
shows the number of process instances by user.