[root@centos7 ~]# cat /root/.bashrc -bash: cat: command not found [root@centos7 ~]# ls -bash: ls: command not found [root@centos7 ~]#
解决过程
ls和cat都是linux的工具，它们都在/bin 这个位置，命令没找到大概是没有去/bin这个地方寻找ls和cat，我们可以打印一下PATH变量承载的是什么东西
[root@centos7 usr]# echo $PATH /usr/local/mysql/bin
这说明，在把mysql的工具添加到环境变量里面的时候，把前面的都覆盖掉了,在 ./bashrc 正确添加mysql环境变量的做法应该是
PATH=${PATH}:/usr/local/mysql/bin
解决方案
[root@centos7 usr]# PATH=${PATH}:/bin
[root@centos7 usr]# echo $PATH
/usr/local/mysql/bin:/bin
之后cat和其他工具都可以使用了，这时应该重新修改/root/.bashrc文件就可以了，我们看看/bin中有什么
[root@centos7 bin]# ls [ gtar rmdir a2p gtbl rnano addr2line gtroff rpcgen alias gunzip rpm apropos gzexe rpm2cpio ar gzip rpmbuild arch h2ph rpmdb as h2xs rpmkeys aserver hdsploader rpmquery aulast head rpmspec aulastlog hexdump rpmverify ausyscall hostid rsyslog-recover-qi.pl auvirt hostname runcon awk hostnamectl run-parts base64 i386 rvi basename iconv rview bash id rvim bashbug idn s2p bashbug-64 igawk scp bg info script bond2team infocmp scriptreplay bootctl infokey sdiff bunzip2 infotocap secon busctl install sed bzcat instmodsh seq bzcmp ionice setarch bzdiff ipcalc setfacl bzgrep ipcmk setfont bzip2 ipcrm setkeycodes bzip2recover ipcs setleds bzless iptables-xml setmetamode bzmore isosize setpriv c++ jobs setsid c2ph join setterm c89 journalctl setup-nsssysinit c99 kbdinfo setup-nsssysinit.sh cal kbd_mode setvtrgb ca-legacy kbdrate sexp-conv captoinfo kdumpctl sftp cat kernel-install sg catchsegv kill sh catman kmod sha1sum cc last sha224sum ccmake lastb sha256sum cd lastlog sha384sum centrino-decode lchfn sha512sum certutil lchsh shasum c++filt ld show-changed-rco chacl ld.bfd showconsolefont chage ldd show-installed chardetect ld.gold showkey chattr less shred chcon lessecho shuf chfn lesskey signtool chgrp lesspipe.sh signver chmod lexgrog size chown libnetcfg skill chrt link slabtop chsh linux32 sleep chvt linux64 slogin cksum linux-boot-prober snice clear ln soelim cmake loadkeys sort cmp loadunimap sotruss cmsutil locale splain col localectl split colcrt localedef sprof colrm logger sqlite3 column login ssh comm loginctl ssh-add command logname ssh-agent coredumpctl look ssh-copy-id cp ls ssh-keygen cpack lsattr ssh-keyscan cpan lsblk ssltap cpio lscpu stat cpp lsinitrd stdbuf cpupower lslocks strings crlutil lslogins strip crontab lsscsi stty csplit lua su csslint-0.6 luac sudo ctest machinectl sudoedit curl mailq sudoreplay cut mailq.postfix sum date make sync db_archive makedb systemctl db_checkpoint man systemd-analyze db_deadlock mandb systemd-ask-password db_dump manpath systemd-cat db_dump185 mapscrn systemd-cgls db_hotbackup mcookie systemd-cgtop dbilogstrip md5sum systemd-coredumpctl dbiprof mesg systemd-delta dbiproxy mixartloader systemd-detect-virt db_load mkdir systemd-escape db_log_verify mkfifo systemd-firstboot db_printlog mkinitrd systemd-hwdb db_recover mknod systemd-inhibit db_replicate mktemp systemd-loginctl db_stat modutil systemd-machine-id-setup db_tuner more systemd-notify db_upgrade mount systemd-nspawn dbus-binding-tool mountpoint systemd-path dbus-cleanup-sockets msgattrib systemd-run dbus-daemon msgcat systemd-stdio-bridge dbus-monitor msgcmp systemd-sysv-convert dbus-send msgcomm systemd-tmpfiles dbus-uuidgen msgconv systemd-tty-ask-password-agent db_verify msgen tabs dd msgexec tac deallocvt msgfilter tail debuginfo-install msgfmt tailf df msggrep tar dgawk msghack taskset diff msginit tbl diff3 msgmerge teamd dir msgunfmt teamdctl dircolors msguniq teamnl dirname mv tee dmesg namei test dnsdomainname nano testgdbm domainname ncurses5-config tic dracut ncursesw5-config time dtrace ndptool timedatectl du needs-restarting timeout dumpkeys neqn tload dwp netstat tmon dwz nettle-hash toe easy_install nettle-lfib-stream top easy_install-2.7 newaliases touch echo newaliases.postfix tput egrep newgrp tr eject ngettext tracepath elfedit nice tracepath6 env nisdomainname troff envsubst nl true eqn nm truncate eu-addr2line nmcli trust eu-ar nm-online tset eu-elfcmp nmtui tsort eu-elflint nmtui-connect tty eu-findtextrel nmtui-edit turbostat eu-make-debug-archive nmtui-hostname tzselect eu-nm nohup udevadm eu-objdump nproc ul eu-ranlib nroff umask eu-readelf nsenter umount eu-size numfmt unalias eu-stack objcopy uname eu-strings objdump unexpand eu-strip od unicode_start eu-unstrip oldfind unicode_stop ex open uniq expand openssl unlink expr openvt unshare factor os-prober unxz fallocate p11-kit unzip false package-cleanup unzipsfx fc passwd update-ca-trust fg paste update-mime-database fgconsole patch uptime fgrep pathchk urlgrabber file perl users find perl5.16.3 usleep find2perl perlbug usx2yloader findmnt perldoc utmpdump find-repos-of-install perlivp uuidgen fipscheck perlthanks VBoxClient fipshmac pgawk VBoxControl firewall-cmd pgrep vdir firewall-offline-cmd pic verifytree flock piconv vi fmt pinentry view fold pinentry-curses vim free ping vimdiff funzip ping6 vimtutor g++ pinky vlock gapplication pk12util vmstat gawk pkaction vxloader gcc pkcheck w gcc-ar pkcs1-conv wait gcc-nm pkexec wall gcc-ranlib pkg-config watch gcore pkill watchgnupg gcov pkla-admin-identities wc gdb pkla-check-authorization wdctl gdb-add-index pkttyagent wget gdbus pl2pm whatis gencat pldd whereis gendiff plymouth which geqn pmap whiptail getconf pod2html who getent pod2man whoami getfacl pod2text write getkeycodes pod2usage x86_64 getopt post-grohtml x86_64-redhat-linux-c++ getopts powernow-k8-decode x86_64-redhat-linux-g++ gettext pr x86_64-redhat-linux-gcc gettext.sh preconv x86_energy_perf_policy gio-querymodules-64 pre-grohtml xargs glib-compile-schemas printenv xgettext gmake printf xmlcatalog gneqn prlimit xmllint gnroff prove xmlwf gpasswd ps xsubpp gperf psed xxd gpg psfaddtable xz gpg2 psfgettable xzcat gpg-agent psfstriptable xzcmp gpgconf psfxtable xzdec gpg-connect-agent pstack xzdiff gpg-error pstruct xzegrep gpgparsemail ptx xzfgrep gpgsplit pwd xzgrep gpgv pwdx xzless gpgv2 pwmake xzmore gpg-zip pwscore yes gpic pydoc ypdomainname gprof python yum grep python2 yum-builddep groff python2.7 yum-config-manager grops ranlib yum-debug-dump grotty raw yum-debug-restore groups read yumdownloader grub2-editenv readelf yum-groups-manager grub2-file readlink zcat grub2-fstest realpath zcmp grub2-glue-efi recode-sr-latin zdiff grub2-kbdcomp rename zegrep grub2-menulst2cfg renice zfgrep grub2-mkfont repoclosure zforce grub2-mkimage repodiff zgrep grub2-mklayout repo-graph zip grub2-mknetdir repomanage zipcloak grub2-mkpasswd-pbkdf2 repoquery zipdetails grub2-mkrelpath repo-rss zipgrep grub2-mkrescue reposync zipinfo grub2-mkstandalone repotrack zipnote grub2-render-label reset zipsplit grub2-script-check resizecons zless grub2-syslinux2cfg rev zmore gsettings rm znew gsoelim rmail zsoelim gstack rmail.postfix