[trouble shooting ] -bash ： cat：command not found
[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
