Looping through the content of a file in Bash. Ask Question Asked 10 years, 4 months ago. Active 3 months ago. Viewed 1.5m times. What is the difference between thee approaches to reading a file that has just one line? Bash while read loop extremely slow compared to cat, why? share improve this answer. edited Oct 26 '18 at 5:40. Often you may want to loop through each line from a file and do something to each line. Yes, you can use Python or other programming language to do that. However, a simple bash script can be extremely useful in looping through lines in a file. Here is how to loop through lines in a []. This function first determines the number of lines in the file, then uses sed to extract line after line, and passes each line as a single string argument to any given function. I suppose this might get really inefficient with large files, but that hasn't been a problem for me so far suggestions on how to improve this welcome of course. The while loop is the best way to read a file line by line in Linux. If you need to read a file line by line and perform some action with each line – then you should use a while read line construction in Bash, as this is the most proper way to do the necessary. In this article i will show the general syntax of the while read line construction in Bash and an example of how to read a file. 15.05.2019 · $ cat file foo bar baz Assume further that I wish to loop through each line with a while. While-loop over lines from variable in bash. Ask Question. please assume that I wish to pass lines stored in a variable rather than lines stored in a file. How can I loop through lines that are saved as a variable without receiving.

H ow do I run shell loop over set of files stored in a current directory or specified directory? You can use for loop easily over a set of shell file under bash or any other UNIX shell using wild card character. 28.07.2015 · These associated data files are single column files, but not all have the same number of columns. For example that data file associated with row 1 might be of form: R1a R1b R1c R1d Is there a way that I can pass the data file above R1a, etc to a for loop within a bash script such that it loops over the lines of the data file and outputs the.

I have a file list.txt that I want to run through line by line, in a loop, in bash. A typical line in list.txt has spaces in. The problem is that the loop contains a "read" command. I want to write this loop in bash rather than something like perl. I can't do it:-Here's how I would usually write a loop to read from a file line by line.