Search a String in File in Linux

If you want to search a particular string in file and want to display the file name. You can refer following Linux commands.

1.    Using grep command recursively search a string.

“grep” command  is very useful command to search the string in files under directory.

# grep –r “string” /path/of/directory

If you want to ignore case sensitiveness use “-i” option with grep command.

# grep –ir “string” /path/of/directory

Example:

[root@paragtesting etc]# grep -ir "nameserver" /etc

/etc/jwhois.conf:       # Catch ARIN nameserver records

/etc/rc1.d/K87named:       if [ -z "$named_c_option" ] && [ -r ${ROOTDIR}/etc/named.caching-nameserver.conf ]; then

/etc/rc1.d/K87named:           named_conf='/etc/named.caching-nameserver.conf';

/etc/cron.daily/0logwatch:   print "           (saves  a  nameserver address-to-name lookup).\n";

/etc/rc4.d/K87named:       if [ -z "$named_c_option" ] && [ -r ${ROOTDIR}/etc/named.caching-nameserver.conf ]; then

/etc/rc4.d/K87named:           named_conf='/etc/named.caching-nameserver.conf';

/etc/rc0.d/K87named:       if [ -z "$named_c_option" ] && [ -r ${ROOTDIR}/etc/named.caching-nameserver.conf ]; then

/etc/rc0.d/K87named:           named_conf='/etc/named.caching-nameserver.conf';

/etc/init.d/named:         if [ -z "$named_c_option" ] && [ -r ${ROOTDIR}/etc/named.caching-nameserver.conf ]; then

/etc/init.d/named:             named_conf='/etc/named.caching-nameserver.conf';

/etc/services:nameserver        42/tcp          name            # IEN 116

/etc/services:nameserver        42/udp          name            # IEN 116

The above command will display the filename and lines in files which contain “string”. If you want to display only filename which contain those string use “-l” option with grep command.

#grep –lir “string” /path/of/directory

Example:

[root@paragtesting etc]# grep -lr "nameserver" /etc

/etc/jwhois.conf

/etc/rc1.d/K87named

/etc/selinux/targeted/modules/active/file_contexts

/etc/selinux/targeted/modules/active/base.linked

/etc/selinux/targeted/modules/active/base.pp

/etc/selinux/targeted/modules/active/file_contexts.template

/etc/selinux/targeted/contexts/files/file_contexts

/etc/cron.daily/0logwatch

/etc/rc4.d/K87named

/etc/rc0.d/K87named

/etc/init.d/named

/etc/services

2.    Find Command:  Recursively search all files for a string.

“find” command is recommend because of speed and ability to deal with filenames that contain spaces. You can use following command with using find to search all files for a particular string in Linux system.

i)             find /path/of/dir  -type f -exec grep -l "string" {} \;

Example:

[root@arogyadbt etc]# find /etc -type f -exec grep -l "prefer-life-time" {} \;

/etc/dhcp6s.conf

ii)            find /path/of/dir  -type f | xargs  grep -l "string"

Example:

[root@arogyadbt etc]# find /etc -type f | xargs  grep -l "prefer-life-time"

/etc/dhcp6s.conf

iii)           find /path/of/dir -type f -print0 | xargs -0 grep –I “string”

Example:

[root@arogyadbt etc]# find /etc -type f -print0 | xargs -0 grep -i "prefer-life-time"

/etc/dhcp6s.conf:#    prefer-life-time 130;

/etc/dhcp6s.conf:#            prefer-life-time 90;

/etc/dhcp6s.conf:#            prefer-life-time 100;

/etc/dhcp6s.conf:#            prefer-life-time 60;