Posts - Page 188 (page 188)
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7 min readIn bash, you can use a combination of commands such as awk or grep to print a line when a certain text pattern changes. One way to achieve this is by using the awk command with the print function to output the lines that match the desired text pattern.For example, if you have a file with lines containing different text patterns, you can use the following command to print a line when the text pattern changes: awk 'a!=$0{print}{a=$0}' filename.
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6 min readTo get memory usage for a specific process ID (PID) in a variable using bash, you can use the following command: mem_usage=$(ps -p $PID -o %mem | awk 'NR==2 {print $1}') Replace $PID with the process ID for which you want to get the memory usage.
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5 min readTo split a string into multiple lines in bash, you can use the tr command to replace a delimiter with a newline character. For example, if you have a string hello|world|foo|bar where | is the delimiter, you can use the following command: echo "hello|world|foo|bar" | tr '|' '\n' This will output: hello world foo bar You can also use the awk command to achieve the same result.
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5 min readTo add a new field in a yaml file using a bash script, you can use tools like yq or sed to manipulate the yaml file. For example, using yq, you can add a new key-value pair to the yaml file like this: yq eval '.newField: "value"' file.yaml > newFile.yaml This will add a new field named "newField" with the value "value" to the yaml file.
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3 min readTo delete added lines between two files in bash, you can use the diff command to compare the two files and then use grep to filter out the added lines. You can do this by running the following command: diff file1.txt file2.txt | grep '^> ' | cut -c3- | comm -23 - <(sort -u file1.txt) | sed '/^>/d' > deleted_lines.txt This command will compare file1.txt and file2.
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4 min readIn Bash, you can assign different outputs to different variables by using command substitution along with the assignment operator. Command substitution allows you to capture the output generated by a command and assign it to a variable.To assign different outputs to different variables, you can use command substitution within a variable assignment statement. For example, you can assign the output of a command to a variable by enclosing the command within $() or backticks (`).
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4 min readTo grep all keywords from an array in a bash script, you can iterate through the array and use the grep command to search for each keyword. You can do this by looping through the array elements and using grep -w to match whole words. Here is an example script that demonstrates this: #.
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5 min readTo properly assign a null value from a bash script to MySQL, you can use the following method. When inserting data into a MySQL database and you want to assign a null value to a column, you can do so by using the keyword "NULL" (in uppercase) without any quotes.
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5 min readTo modify printf with the last -10 command in bash, you can use the !! shortcut to access the previous command and then pipe the output to printf with the desired format. For example, you can use the following command to print the last -10 command in a specific format: !! | tail -10 | printf "%s\n" This will retrieve the last -10 command from the command history, extract only the last 10 lines using tail, and then print them using printf with the specified format.
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4 min readYou can check for the latest available Python 3.x version from bash by using the command curl to make a request to the official Python website and grep to filter out the latest version number. You can use the following command:curl -s 'https://www.python.org/downloads/' | grep -o -E 'Python [0-9]+\.[0-9]+\.
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4 min readIn Bash, you can check if an argument starts with "--" by using the built-in parameter expansion feature. You can access the value of each argument by referencing it as $1, $2, $3, and so on.
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4 min readTo add decimal values in bash, you can use the bc command. This command allows you to perform calculations with decimal numbers. Here's a simple example of how you can add two decimal values in bash using the bc command:result=$(echo "3.14 + 2.5" | bc) echo $resultIn this example, the echo command is used to provide the calculation "3.14 + 2.5" to the bc command. The bc command then performs the addition and stores the result in the variable result.