if you ever need to run grep command over multiple files then use this style:
find / -xdev -type f -print0 | xargs -0 grep -H "text_to_search_for"
What this actually does is make a list of every file on the system, and then for each file, execute grepwith the given arguments and the name of each file.
The -xdev argument tells find that it must ignore other filesystems - this is good for avoiding special filesystems such as /proc. However it will also ignore normal filesystems too - so if, for example, your /home folder is on a different partition, it won't be searched - you would need to say find / /home -xdev ....
-type f means search for files only, so directories, devices and other special files are ignored (it will still recurse into directories and execute grep on the files within - it just won't execute grep on the directory itself, which wouldn't work anyway). And the -H option to grep tells it to always print the filename in its output.
find accepts all sorts of options to filter the list of files. For example, -name '*.txt' processes only files ending in .txt. -size -2M means files that are smaller than 2 megabytes. -mtime -5 means files modified in the last five days. Join these together with -a for and and -o for or, and use '('parentheses ')' to group expressions (in quotes to prevent the shell from interpreting them). So for example:
find / -xdev '(' -type f -a -name '*.txt' -a -size -2M -a -mtime -5 ')' -print0 | xargs -0 grep -H "text_to_search_for"
find / -xdev -type f -print0 | xargs -0 grep -H "text_to_search_for"
What this actually does is make a list of every file on the system, and then for each file, execute grepwith the given arguments and the name of each file.
The -xdev argument tells find that it must ignore other filesystems - this is good for avoiding special filesystems such as /proc. However it will also ignore normal filesystems too - so if, for example, your /home folder is on a different partition, it won't be searched - you would need to say find / /home -xdev ....
-type f means search for files only, so directories, devices and other special files are ignored (it will still recurse into directories and execute grep on the files within - it just won't execute grep on the directory itself, which wouldn't work anyway). And the -H option to grep tells it to always print the filename in its output.
find accepts all sorts of options to filter the list of files. For example, -name '*.txt' processes only files ending in .txt. -size -2M means files that are smaller than 2 megabytes. -mtime -5 means files modified in the last five days. Join these together with -a for and and -o for or, and use '('parentheses ')' to group expressions (in quotes to prevent the shell from interpreting them). So for example:
find / -xdev '(' -type f -a -name '*.txt' -a -size -2M -a -mtime -5 ')' -print0 | xargs -0 grep -H "text_to_search_for"
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