How to search history commands very effectively in bash shell command line? Just enter CTRL+r The function of above is: (reverse-i-search)`’: It is very fast and efficient. Answered by harryxiyou.
Posts tagged Bash
148 posts in total.
Why I cannot login remote server with its root
# ssh root@192.168.122.96 root@192.168.122.96’s password: Permission denied, please try again. Do according to [1]. NOTE: on Ubuntu, remember to restart ssh service like this “sudo restart ssh”. [1] https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/v2v_guide/preparation_before_the_p2v_migration-enable_root_login_over_ssh Answered by harryxiyou.
How to judge whether its STDERR is redirected to a file in a Bash script on Linux?
Within a Bash script, how to judge whether its STDERR is redirected to a file in Bash on Linux? For example, ./script.sh /tmp/log 2>&1 Can script.sh detect that its STDERR is redirected? Knowing the destination file is better. To test whether a script’s STDERR (or STDOUT) is redirected to a file, check by [[ -f […]
How can I login without password and run command in server at a local machine remotely?
Login without PWD is fast and efficient. Running commands in server from local machine also have these benefits. login without PWD: add PC A’s public key to PC B’s authorized keys. > a@A:~> cat .ssh/id_rsa.pub | ssh b@B ‘cat >> .ssh/authorized_keys’ > b@B’s password: Run command remotely ssh root@MachineB “ls” NOTE: running commands remotely is […]
how to set linux date and time in commands
how to set linux date and time in commands For example, to change date to 14 Nov 2017 11:57:00, the command would be, $ sudo date –set “14 Nov 2017 11:57:00” Tue Nov 14 11:57:00 HKT 2017 Answered by harryxiyou.
How to print all fields after a certain field with awk on Linux?
How to print all fields after a certain field with awk on Linux? Say, I want to print out all fields after field $3: a b c d e f a b b b a a c d should be transformed to d e f b d You may use a for loop in awk […]
How to add a prefix string at the beginning of each line in Bash shell script on Linux?
How to add a prefix string at the beginning of each line in Bash shell script on Linux? For example, assume we have a file a.txt: line 1 line 2 I want to have, pre line 1 pre line 2 You may use sed, the stream editor for filtering and transforming text: sed -e ‘s/^/pre […]
How to detect whether a file is being written by any other process in Linux?
How to detect whether a file is being written by any other process in Linux? Before a program open a file to processes it, it wants to ensure no other processes are writing to it. Here, we are sure after the files are written and closed, they will not be written any more. Hence, one-time […]
How to get the highest temperature from all sensors in a server on Linux?
It is useful to monitor a server node’s temporary. Among all the sensors’ temperatures, the higher one may be a very important one. How to get the highest temperature from all sensors in a server on Linux? You can use this command to get the the highest temperature from all sensors in a server on […]
How to split a gzip file to several small ones on Linux?
I have a very large (e.g. 100GB) .gz file and would like to split it into smaller files like 8GB/each for storage/copying. How to split a gzip file to several small ones on Linux? You may use the tool split to split a file by sizes. An example to split a large.tgz to at most […]
How to get the mtime of a file on Linux?
How to get the mtime of a file on Linux from the file’s path? You can use stat to get the file status including the mtime: %y time of last modification, human-readable %Y time of last modification, seconds since Epoch As an example, $ stat -c %y ./file 2017-06-26 13:33:06.764042064 +0800 $ stat -c %Y […]
How to print a line to STDERR and STDOUT in Bash?
In Bash, how to print a string as a line to STDOUT? That is, the string and the newline character, nicely? And similarly, how to print the line to STDERR? In Bash, you can simply use the echo command: echo “your message here” or echo your message here Examples: $ echo the message here the […]
How to get the running process’ parent process’ ID in C / C++?
How to get the running process’ parent process’ ID in C / C++? In C and C++, you can call the getppid() library function which is a function from the POSIX library. #include <sys/types.h> #include <unistd.h> pid_t getppid(void); getppid() returns the process ID of the parent of the calling process. Example usage: getppid.c #include <stdio.h> […]
How to get the running process’ parent process’ ID in Bash?
How to get the running process’ parent process’ ID in Bash? In Bash, you can get the parent process’s pid from the variable PPID. Note that in a (…) subshell, the $$ stores the subshell’s parent shell pid actually. Answered by dtivl.
How to debug a Bash script?
How to debug a Bash script if it has some bugs? Common techniques like printing varibles out for checking apply for bash too. For bash, I usually use 2 bash-specific techniques. Add set -o errexit to the beginning of the scripterrexit makes bash exit immediately if one statement’s return code is not 0. This way, […]
How to get the running process’ pid in Bash?
How to get the running process’ pid in Bash? In Bash, you can get the process ID from the variable $$. Note that in a subshell invoked by ‘(…)‘, $$ is actually the parent process’ pid. In Bash 4, you can also use $BASHPID to get the process pid. Answered by dtivl.
How to split a string by string in Bash?
How to split a string by string in Bash? For example, “a string separated by space” => [“a”, “string”, “separated”, “by”, “space”] and “a,string,separated,by,comma” => [“a”, “string”, “separated”, “by”, “comma”] You can convert a string to an array using the grammar like inarr=(${a}) If the delimiter is not space and delimiter is a single character […]
How to convert epoch timestamp to human readable date format in Bash?
In Bash, how to convert an epoch timestamp to a human readable date format? In Bash, you can use the date command’s -d option: date -d @<your epoch> Here @ specifies the epoch timestamp. One example: $ date -d @1490157520.05 Wed Mar 22 12:38:40 HKT 2017 Answered by dtivl.
How to get the hostname of the node in Bash?
In Bash, how to get the hostname of the node running the program? In Bash, you can get the hostname of the node in at least 2 ways: Use the variable $HOSTNAME. Get the hostname by command hostname. Get the content of /proc/sys/kernel/hostname Example: $ echo $HOSTNAME host01 $ hs=`hostname` $ echo $hs host01 $ […]
How to get the epoch timestamp in Bash?
In Bash, how to get the epoch timestamp, the number of seconds passed since the epoch? In Bash, you can call the date command with format option “+%s”: date +%s Here, “%s” means: %s seconds since 1970-01-01 00:00:00 UTC Answered by dtivl.
